Explicit-save UX: Save button, dirty indicator, quit warning, project title, native bridge hook (#403 Phase A)

[maboa]

Part of the #403/#404 Phase A push. HLE moves to an explicit-save document model (matching Glider): the .hyperaudio file is the durable copy, OPFS is crash recovery only.

1. Save button in the navbar with a dirty indicator (dot/filled state), wired to the same save path as FILE → Save Project; ⌘/Ctrl-S binding.
2. beforeunload warning when dirty — the quit-without-saving guard.
3. Project title source: Save/open projects as a single .hyperaudio file (#403) #404 read #save-localstorage-filename as the title; that field was deleted with the legacy dialogs (Simplify the FILE-menu save/load dialogs once Recents autosaves #436/Remove the FILE-menu Save/Load Local Storage dialogs #439). Add an editable project-title field (defaulting from the opened filename or media name) and use it for the suggested save filename.
4. Native bridge hook: before falling back to <a download>, offer the finished archive to a registered bridge (e.g. window.hyperaudioProjectBridge.save(blob, suggestedName) or a cancelable custom event carrying the Blob). An embedding native app registers the bridge at startup and writes through its own filesystem — retiring injected save UI and keeping one save path across web and native. Document the hook's shape alongside the format spec.
5. The blocking confirm() dialogs in the save/open flow can become in-app modals later — not blocking for Phase A.

[maboa]

Landed on the #404 branch through d811e37 + follow-up, shaped by design review:

• Save button: btn-primary immediately left of the export button, matching the GliderMac injected button exactly (classes, icon, dot treatment — primary-content dot ringed in primary, tooltip "Save project (⌘S)"), so retiring the injection (glider#173) is visually seamless. ⌘/Ctrl-S bound.
• beforeunload quit guard, armed only when the session holds unsaved work; e2e asserts arming/disarming via cancelable synthetic events.
• Bridge hook: window.hyperaudioProjectBridge.save(blob, suggestedName) intercepts before the download fallback; returning false declines. Clean-marking flows through bridge saves; e2e-covered.
• Menu simplification: FILE loses the Project section entirely — the button covers saving; opening became "Import Project (.hyperaudio)" atop the Export/Import submenu.
• No title field / no project row (both cut in review): the auto-added Recents entry's highlight indicates the current doc; the title round-trips via texts.title+session, renaming UI returns with the Delete the legacy localStorage/IndexedDB storage layer and the Recents UI (#403 Phase A) #451 panel redesign. gather() still prefers a #project-title element if one ever exists.

[maboa]

Shipped in the Phase A merges and verified against current main: navbar Save button with dirty indicator, ⌘/Ctrl-S, beforeunload warning when dirty, the editable #project-title field feeding save filenames, and the window.hyperaudioProjectBridge native hook. Closing.