feat(tagger): real byte progress for model download instead of a spinner

The 1.3 GB model.onnx downloaded via hf-hub's repo.get() and the ONNX
runtime DLLs via a read_to_end — neither reported bytes, so the user saw
only an indeterminate spinner on a multi-minute download.

- tagger model files now download via repo.download_with_progress with a
  HubProgress adapter over hf-hub's Progress trait (throttled 200ms events
  carrying downloaded/total bytes)
- captioner's nuget DLL download streams in 64 KB chunks, parsing
  content-length, and reports per-chunk byte progress
- TaggerModelProgress carries downloaded_bytes/total_bytes; onboarding and
  Settings show a determinate bar plus 'X MB / Y MB' for the current file

src-tauri/src/captioner.rs

@@ -669,20 +669,45 @@ pub fn ensure_onnx_runtime(local_dir: &Path) -> Result<()> {
     Ok(())
 }
 
-/// Download any ONNX Runtime DLLs that are missing from `local_dir`. Unlike
+/// Download any ONNX Runtime DLLs missing from `local_dir`, reporting per-file
+/// byte progress as `(short_label, downloaded_bytes, total_bytes)`.
+/// `total_bytes` is `None` when the server omits Content-Length. Unlike
 /// `ensure_onnx_runtime` (init only), this actually provisions the files —
-/// callers that can run on a clean install must call this first.
-pub fn provision_onnx_runtime(local_dir: &Path) -> Result<()> {
+/// callers that can run on a clean install must call this first. The callback
+/// fires per chunk; callers should throttle.
+pub fn provision_onnx_runtime_with_progress(
+    local_dir: &Path,
+    mut on_progress: impl FnMut(&str, u64, Option<u64>),
+) -> Result<()> {
     for (destination_file, source_url, archive_path) in ONNX_RUNTIME_FILES {
         let destination = local_dir.join(destination_file);
         if destination.exists() {
             continue;
         }
-        download_nuget_file(source_url, archive_path, &destination)?;
+        // Strip the "onnxruntime/" prefix for a clean label.
+        let label = destination_file
+            .rsplit('/')
+            .next()
+            .unwrap_or(destination_file);
+        download_nuget_file(
+            source_url,
+            archive_path,
+            &destination,
+            |downloaded, total| on_progress(label, downloaded, total),
+        )?;
     }
     Ok(())
 }
 
+/// Number of ONNX Runtime DLLs still missing from `local_dir` (for progress
+/// step counts before downloading).
+pub fn missing_onnx_runtime_count(local_dir: &Path) -> usize {
+    ONNX_RUNTIME_FILES
+        .iter()
+        .filter(|(destination_file, _, _)| !local_dir.join(destination_file).exists())
+        .count()
+}
+
 fn download_onnx_runtime_files(local_dir: &Path) -> Result<()> {
     if !cfg!(target_os = "windows") {
         anyhow::bail!(
@@ -692,22 +717,43 @@ fn download_onnx_runtime_files(local_dir: &Path) -> Result<()> {
 
     for (destination_file, source_url, archive_path) in ONNX_RUNTIME_FILES {
         let destination = local_dir.join(destination_file);
-        download_nuget_file(source_url, archive_path, &destination)?;
+        download_nuget_file(source_url, archive_path, &destination, |_, _| {})?;
     }
 
     Ok(())
 }
 
-fn download_nuget_file(source_url: &str, archive_path: &str, destination: &Path) -> Result<()> {
+fn download_nuget_file(
+    source_url: &str,
+    archive_path: &str,
+    destination: &Path,
+    mut on_progress: impl FnMut(u64, Option<u64>),
+) -> Result<()> {
     let mut response = ureq::get(source_url)
         .call()
         .map_err(|error| anyhow::anyhow!("{error}"))?;
-    let mut bytes = Vec::new();
-    response
-        .body_mut()
-        .as_reader()
-        .read_to_end(&mut bytes)
-        .map_err(|error| anyhow::anyhow!("{error}"))?;
+    let total_bytes = response
+        .headers()
+        .get("content-length")
+        .and_then(|value| value.to_str().ok())
+        .and_then(|value| value.parse::<u64>().ok());
+
+    // Stream into memory (the zip reader needs Seek) while reporting bytes.
+    let mut bytes = Vec::with_capacity(total_bytes.unwrap_or(0) as usize);
+    let mut reader = response.body_mut().as_reader();
+    let mut buffer = [0u8; 64 * 1024];
+    let mut downloaded = 0u64;
+    loop {
+        let read = reader
+            .read(&mut buffer)
+            .map_err(|error| anyhow::anyhow!("{error}"))?;
+        if read == 0 {
+            break;
+        }
+        bytes.extend_from_slice(&buffer[..read]);
+        downloaded += read as u64;
+        on_progress(downloaded, total_bytes);
+    }
 
     let mut archive = zip::ZipArchive::new(Cursor::new(bytes))?;
     let mut dll = archive.by_name(archive_path)?;

src-tauri/src/tagger.rs

@@ -87,9 +87,63 @@ pub struct TaggerModelProgress {
     pub total_files: usize,
     pub completed_files: usize,
     pub current_file: Option<String>,
+    // Byte progress for the file currently downloading. None for files whose
+    // size isn't known up front (or between files).
+    pub downloaded_bytes: Option<u64>,
+    pub total_bytes: Option<u64>,
     pub done: bool,
 }
 
+/// Adapts hf-hub's `Progress` trait to throttled `tagger-model-progress`
+/// events so the 1.3 GB model download reports real bytes, not a spinner.
+struct HubProgress<'a, F: Fn(TaggerModelProgress)> {
+    emit: &'a F,
+    total_files: usize,
+    completed_files: usize,
+    current_file: String,
+    downloaded: u64,
+    total: u64,
+    last_emit: Instant,
+}
+
+impl<F: Fn(TaggerModelProgress)> hf_hub::api::Progress for HubProgress<'_, F> {
+    fn init(&mut self, size: usize, _filename: &str) {
+        self.total = size as u64;
+        self.downloaded = 0;
+        self.last_emit = Instant::now();
+        (self.emit)(self.snapshot(false));
+    }
+
+    fn update(&mut self, size: usize) {
+        self.downloaded = self.downloaded.saturating_add(size as u64);
+        if self.last_emit.elapsed() >= std::time::Duration::from_millis(200) {
+            self.last_emit = Instant::now();
+            (self.emit)(self.snapshot(false));
+        }
+    }
+
+    fn finish(&mut self) {
+        (self.emit)(self.snapshot(false));
+    }
+}
+
+impl<F: Fn(TaggerModelProgress)> HubProgress<'_, F> {
+    fn snapshot(&self, done: bool) -> TaggerModelProgress {
+        TaggerModelProgress {
+            total_files: self.total_files,
+            completed_files: self.completed_files,
+            current_file: Some(self.current_file.clone()),
+            downloaded_bytes: Some(self.downloaded),
+            total_bytes: if self.total > 0 {
+                Some(self.total)
+            } else {
+                None
+            },
+            done,
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Runtime probe types exposed to the frontend
 // ---------------------------------------------------------------------------
@@ -250,59 +304,83 @@ pub fn prepare_tagger_model_with_progress(
     let local_dir = model_dir(app_data_dir);
     std::fs::create_dir_all(&local_dir)?;
 
-    // Ensure the shared ONNX runtime DLLs are present. The tagger shares
-    // them with the captioner; download them here so the tagger is fully
-    // functional even on a clean install where the caption model has never
-    // been downloaded (ensure_onnx_runtime only initializes, never downloads).
+    // The tagger shares the ONNX runtime DLLs with the captioner; download
+    // them here so the tagger works even on a clean install where the caption
+    // model has never been fetched (ensure_onnx_runtime only initializes).
+    const DOWNLOAD_FILES: &[&str] = &["model.onnx", "selected_tags.csv"];
     let caption_model_dir = crate::captioner::model_dir(app_data_dir);
     std::fs::create_dir_all(&caption_model_dir)?;
-    crate::captioner::provision_onnx_runtime(&caption_model_dir)?;
-    crate::captioner::ensure_onnx_runtime(&caption_model_dir)?;
 
-    // Download the two tagger-specific files.
-    const DOWNLOAD_FILES: &[&str] = &["model.onnx", "selected_tags.csv"];
-
-    let api = Api::new()?;
-    let repo = api.repo(Repo::new(WD_TAGGER_MODEL_ID.to_string(), RepoType::Model));
-
-    let mut completed_files = DOWNLOAD_FILES
+    // Unified step count across DLLs and tagger files so the bar is coherent.
+    let dll_count = crate::captioner::missing_onnx_runtime_count(&caption_model_dir);
+    let model_pending = DOWNLOAD_FILES
         .iter()
-        .filter(|file| local_dir.join(file).exists())
+        .filter(|file| !local_dir.join(file).exists())
         .count();
+    let total_files = dll_count + model_pending;
+    let mut completed_files = 0usize;
 
     emit_progress(TaggerModelProgress {
-        total_files: DOWNLOAD_FILES.len(),
+        total_files,
         completed_files,
         current_file: None,
-        done: completed_files == DOWNLOAD_FILES.len(),
+        downloaded_bytes: None,
+        total_bytes: None,
+        done: total_files == 0,
     });
 
+    // ── ONNX runtime DLLs (small, but non-trivial on a slow link) ──
+    {
+        let mut last_emit = Instant::now() - std::time::Duration::from_secs(1);
+        crate::captioner::provision_onnx_runtime_with_progress(
+            &caption_model_dir,
+            |label, downloaded, total| {
+                if last_emit.elapsed() >= std::time::Duration::from_millis(200) {
+                    last_emit = Instant::now();
+                    emit_progress(TaggerModelProgress {
+                        total_files,
+                        completed_files,
+                        current_file: Some(format!("ONNX Runtime: {label}")),
+                        downloaded_bytes: Some(downloaded),
+                        total_bytes: total,
+                        done: false,
+                    });
+                }
+            },
+        )?;
+        completed_files += dll_count;
+    }
+    crate::captioner::ensure_onnx_runtime(&caption_model_dir)?;
+
+    // ── Tagger model files (model.onnx is ~1.3 GB) ──
+    let api = Api::new()?;
+    let repo = api.repo(Repo::new(WD_TAGGER_MODEL_ID.to_string(), RepoType::Model));
+
     for file in DOWNLOAD_FILES {
         let destination = local_dir.join(file);
         if destination.exists() {
             continue;
         }
-        emit_progress(TaggerModelProgress {
-            total_files: DOWNLOAD_FILES.len(),
+        let progress = HubProgress {
+            emit: &emit_progress,
+            total_files,
             completed_files,
-            current_file: Some((*file).to_string()),
-            done: false,
-        });
-        let cached = repo.get(file)?;
+            current_file: (*file).to_string(),
+            downloaded: 0,
+            total: 0,
+            last_emit: Instant::now(),
+        };
+        let cached = repo.download_with_progress(file, progress)?;
         std::fs::copy(cached, destination)?;
         completed_files += 1;
-        emit_progress(TaggerModelProgress {
-            total_files: DOWNLOAD_FILES.len(),
-            completed_files,
-            current_file: Some((*file).to_string()),
-            done: completed_files == DOWNLOAD_FILES.len(),
-        });
     }
 
     emit_progress(TaggerModelProgress {
-        total_files: DOWNLOAD_FILES.len(),
+        total_files,
         completed_files,
         current_file: None,
+        downloaded_bytes: None,
+        total_bytes: None,
         done: true,
     });