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/components/WhatsNewModal.tsx

@@ -0,0 +1,197 @@
+import { useEffect, useState, type ReactNode } from "react";
+import { AnimatePresence, motion } from "framer-motion";
+import { openUrl } from "@tauri-apps/plugin-opener";
+import { useGalleryStore } from "../store";
+import { getChangelogForVersion, type ChangelogSection } from "../changelog";
+
+const CHANGELOG_URL = "https://github.com/JezzWTF/phokus/blob/main/CHANGELOG.md";
+
+// Per-section accent. These all use the standard colour scale, which the
+// subtle-light theme re-maps to readable dark shades via CSS variables — so no
+// `light-theme:` overrides are needed (or wanted) here. See the theme note in
+// index.css: `bg-white`/`text-white` deliberately become *dark* in light mode,
+// so neutral surfaces must use the gray scale and trust the remap.
+const SECTION_STYLES: Record<string, { label: string; dot: string }> = {
+  Added: { label: "text-emerald-300", dot: "bg-emerald-400/80" },
+  Changed: { label: "text-sky-300", dot: "bg-sky-300/80" },
+  Fixed: { label: "text-amber-300", dot: "bg-amber-400/80" },
+  Removed: { label: "text-rose-300", dot: "bg-rose-400/80" },
+  Security: { label: "text-violet-300", dot: "bg-violet-400/80" },
+};
+
+const NEUTRAL_STYLE = { label: "text-gray-300", dot: "bg-gray-400/70" };
+
+// Render the small amount of inline markdown the changelog uses: **bold** and
+// `code`. Anything else passes through as plain text.
+function renderInline(text: string): ReactNode[] {
+  const nodes: ReactNode[] = [];
+  const regex = /\*\*(.+?)\*\*|`([^`]+)`/g;
+  let lastIndex = 0;
+  let key = 0;
+  let match: RegExpExecArray | null;
+  while ((match = regex.exec(text)) !== null) {
+    if (match.index > lastIndex) {
+      nodes.push(text.slice(lastIndex, match.index));
+    }
+    if (match[1] !== undefined) {
+      nodes.push(
+        <strong key={key++} className="font-semibold text-white">
+          {match[1]}
+        </strong>,
+      );
+    } else if (match[2] !== undefined) {
+      nodes.push(
+        <code key={key++} className="rounded bg-white/10 px-1 py-0.5 text-[12px] text-gray-200">
+          {match[2]}
+        </code>,
+      );
+    }
+    lastIndex = regex.lastIndex;
+  }
+  if (lastIndex < text.length) {
+    nodes.push(text.slice(lastIndex));
+  }
+  return nodes;
+}
+
+function Section({ section }: { section: ChangelogSection }) {
+  const style = SECTION_STYLES[section.title] ?? NEUTRAL_STYLE;
+  const [open, setOpen] = useState(true);
+
+  return (
+    <section>
+      <button
+        type="button"
+        onClick={() => setOpen((value) => !value)}
+        className="flex w-full items-center gap-2 text-left"
+        aria-expanded={open}
+      >
+        <svg
+          className={`h-3 w-3 shrink-0 text-gray-600 transition-transform ${open ? "rotate-90" : ""}`}
+          fill="none"
+          viewBox="0 0 24 24"
+          stroke="currentColor"
+        >
+          <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2.5} d="M9 5l7 7-7 7" />
+        </svg>
+        <span className={`text-[11px] font-semibold uppercase tracking-[0.1em] ${style.label}`}>{section.title}</span>
+        <span className="text-[11px] font-medium text-gray-600">{section.items.length}</span>
+      </button>
+      <AnimatePresence initial={false}>
+        {open ? (
+          <motion.div
+            initial={{ height: 0, opacity: 0 }}
+            animate={{ height: "auto", opacity: 1 }}
+            exit={{ height: 0, opacity: 0 }}
+            transition={{ duration: 0.18 }}
+            className="overflow-hidden"
+          >
+            <ul className="mt-2.5 space-y-2.5 pl-5">
+              {section.items.map((item, index) => (
+                <li key={index} className="flex gap-3">
+                  <span className={`mt-[7px] h-1.5 w-1.5 shrink-0 rounded-full ${style.dot}`} />
+                  <p className="text-[13px] leading-relaxed text-gray-400">
+                    {item.lead ? (
+                      <>
+                        <span className="font-semibold text-gray-100">{item.lead}</span>
+                        {item.body ? <span> — {renderInline(item.body)}</span> : null}
+                      </>
+                    ) : (
+                      renderInline(item.body)
+                    )}
+                  </p>
+                </li>
+              ))}
+            </ul>
+          </motion.div>
+        ) : null}
+      </AnimatePresence>
+    </section>
+  );
+}
+
+export function WhatsNewModal() {
+  const whatsNewOpen = useGalleryStore((s) => s.whatsNewOpen);
+  const closeWhatsNew = useGalleryStore((s) => s.closeWhatsNew);
+  const appVersion = useGalleryStore((s) => s.appVersion);
+
+  const entry = getChangelogForVersion(appVersion);
+
+  useEffect(() => {
+    if (!whatsNewOpen) return;
+    const handleKeyDown = (event: KeyboardEvent) => {
+      if (event.key === "Escape") closeWhatsNew();
+    };
+    window.addEventListener("keydown", handleKeyDown);
+    return () => window.removeEventListener("keydown", handleKeyDown);
+  }, [whatsNewOpen, closeWhatsNew]);
+
+  return (
+    <AnimatePresence>
+      {whatsNewOpen ? (
+        <motion.div
+          className="fixed inset-0 z-[90] flex items-center justify-center bg-black/65 px-6 backdrop-blur-sm"
+          onClick={closeWhatsNew}
+          initial={{ opacity: 0 }}
+          animate={{ opacity: 1 }}
+          exit={{ opacity: 0 }}
+          transition={{ duration: 0.15 }}
+        >
+          <motion.div
+            className="relative flex max-h-[min(82vh,760px)] w-[min(88vw,560px)] flex-col overflow-hidden rounded-lg border border-white/10 bg-gray-950 shadow-2xl shadow-black/60"
+            onClick={(event) => event.stopPropagation()}
+            initial={{ opacity: 0, scale: 0.97, y: 8 }}
+            animate={{ opacity: 1, scale: 1, y: 0 }}
+            exit={{ opacity: 0, scale: 0.98, y: 6 }}
+            transition={{ duration: 0.16 }}
+          >
+            <div className="flex items-start justify-between gap-4 border-b border-white/[0.07] px-6 py-5">
+              <div>
+                <p className="text-[11px] font-semibold uppercase tracking-[0.12em] text-emerald-300">What's new</p>
+                <h3 className="mt-1 text-lg font-semibold text-white">
+                  Phokus v{entry?.version ?? appVersion ?? "—"}
+                </h3>
+                {entry?.date ? <p className="mt-0.5 text-xs text-gray-600">Released {entry.date}</p> : null}
+              </div>
+              <button
+                className="rounded-md p-1.5 text-gray-500 transition-colors hover:bg-white/[0.06] hover:text-white"
+                onClick={closeWhatsNew}
+                title="Close"
+              >
+                <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />
+                </svg>
+              </button>
+            </div>
+
+            <div className="min-h-0 flex-1 space-y-6 overflow-y-auto px-6 py-5">
+              {entry && entry.sections.length > 0 ? (
+                entry.sections.map((section) => <Section key={section.title} section={section} />)
+              ) : (
+                <p className="text-sm text-gray-500">
+                  Release notes for this version aren't available in-app. See the full changelog on GitHub.
+                </p>
+              )}
+            </div>
+
+            <div className="flex items-center justify-between gap-4 border-t border-white/[0.07] px-6 py-4">
+              <button
+                type="button"
+                onClick={() => void openUrl(CHANGELOG_URL)}
+                className="text-xs text-gray-500 transition-colors hover:text-gray-300"
+              >
+                Full changelog ↗
+              </button>
+              <button
+                className="rounded-md border border-emerald-400/35 bg-emerald-500/15 px-3.5 py-1.5 text-xs text-emerald-200 transition-colors hover:bg-emerald-500/25"
+                onClick={closeWhatsNew}
+              >
+                Got it
+              </button>
+            </div>
+          </motion.div>
+        </motion.div>
+      ) : null}
+    </AnimatePresence>
+  );
+}