feat: What's New screen + updater progress, plus light-theme fixes

Post-update UX for the next release (0.1.2):

- What's New: after a version change, greet the user with a toast that opens
  an in-app release-notes screen (collapsible Added/Changed/Fixed sections)
  sourced from the bundled CHANGELOG.md, reopenable from Settings -> Updates.
  Backed by a last_seen_version settings file (get/set_last_seen_version
  commands) that distinguishes upgrades from fresh installs.
- Updater: the download/install progress toast now reappears when an update is
  started from the title-bar indicator or Settings after the prompt was
  dismissed; Settings -> Updates gains a real progress bar with a percentage.
- Light theme: fix the recurring subtle-light breakage. Neutral surfaces now
  rely on the CSS-variable remap instead of light-theme:bg-white (which forced
  surfaces dark because --color-white is remapped dark); the green action
  buttons drop the broken light-theme:hover:bg-emerald-200 (remapped dark,
  unreadable on hover) for an override-free emerald-500 tint that auto-themes,
  across the updater, What's New, and onboarding.
- Debug panel: add What's New triggers (toast / modal / reset).

src/changelog.ts

@@ -0,0 +1,112 @@
+// Parses the project CHANGELOG.md (imported raw at build time) into structured
+// data so the "What's New" UI can render it nicely instead of dumping markdown.
+// Keeping the changelog as the single source of truth means there's no separate
+// per-release copy to maintain — whatever ships in CHANGELOG.md is what users see.
+import changelogRaw from "../CHANGELOG.md?raw";
+
+export interface ChangelogItem {
+  /** The bold lead-in at the start of a bullet (e.g. "Custom multi-folder picker"), if any. */
+  lead: string | null;
+  /** The remaining descriptive text. May still contain inline `code` / **bold** markers. */
+  body: string;
+}
+
+export interface ChangelogSection {
+  /** "Added" | "Changed" | "Fixed" | "Removed" | "Deprecated" | "Security" */
+  title: string;
+  items: ChangelogItem[];
+}
+
+export interface ChangelogEntry {
+  version: string;
+  date: string | null;
+  sections: ChangelogSection[];
+}
+
+// "## [0.1.1] — 2026-06-23" / "## [Unreleased]"
+const VERSION_HEADING = /^##\s+\[([^\]]+)\]\s*(?:[—–-]\s*(.+?)\s*)?$/;
+// "### Added"
+const SECTION_HEADING = /^###\s+(.+?)\s*$/;
+// "- bullet text"
+const BULLET = /^[-*]\s+(.*)$/;
+// Leading "**Title**" optionally followed by an em dash, used as the item's lead-in.
+// (Item text is whitespace-collapsed before matching, so no dotAll flag needed.)
+const LEAD = /^\*\*(.+?)\*\*\s*(?:[—–-]\s*)?(.*)$/;
+
+function toItem(text: string): ChangelogItem {
+  const collapsed = text.replace(/\s+/g, " ").trim();
+  const match = collapsed.match(LEAD);
+  if (match) {
+    return { lead: match[1].trim(), body: match[2].trim() };
+  }
+  return { lead: null, body: collapsed };
+}
+
+function parseChangelog(raw: string): ChangelogEntry[] {
+  const lines = raw.split(/\r?\n/);
+  const entries: ChangelogEntry[] = [];
+
+  let entry: ChangelogEntry | null = null;
+  let section: ChangelogSection | null = null;
+  let buffer: string[] = [];
+
+  const flushItem = () => {
+    if (section && buffer.length > 0) {
+      section.items.push(toItem(buffer.join(" ")));
+    }
+    buffer = [];
+  };
+
+  for (const line of lines) {
+    const versionMatch = line.match(VERSION_HEADING);
+    if (versionMatch) {
+      flushItem();
+      section = null;
+      entry = { version: versionMatch[1].trim(), date: versionMatch[2]?.trim() ?? null, sections: [] };
+      entries.push(entry);
+      continue;
+    }
+
+    // Stop collecting once we leave the changelog body (e.g. link-reference defs at EOF).
+    if (!entry) continue;
+
+    const sectionMatch = line.match(SECTION_HEADING);
+    if (sectionMatch) {
+      flushItem();
+      section = { title: sectionMatch[1].trim(), items: [] };
+      entry.sections.push(section);
+      continue;
+    }
+
+    const bulletMatch = line.match(BULLET);
+    if (bulletMatch) {
+      flushItem();
+      buffer.push(bulletMatch[1]);
+      continue;
+    }
+
+    if (line.trim() === "") {
+      // A blank line ends a (possibly wrapped) multi-line bullet.
+      flushItem();
+      continue;
+    }
+
+    // Indented continuation of the current wrapped bullet.
+    if (buffer.length > 0) {
+      buffer.push(line.trim());
+    }
+  }
+
+  flushItem();
+  return entries.map((e) => ({ ...e, sections: e.sections.filter((s) => s.items.length > 0) }));
+}
+
+const ENTRIES = parseChangelog(changelogRaw);
+
+export function getChangelogForVersion(version: string | null | undefined): ChangelogEntry | null {
+  if (!version) return null;
+  const normalized = version.replace(/^v/, "");
+  // Never surface the in-progress [Unreleased] section to users.
+  if (normalized.toLowerCase() === "unreleased") return null;
+  return ENTRIES.find((e) => e.version.replace(/^v/, "") === normalized) ?? null;
+}