Bring spec and README up to date

The spec still listed undo, the eraser, colours and smoothing as
missing. Describe the ink engine and palm rejection as built (draw vs
navigate intents, settings toggles, cancelled pointers), the plus
buttons, fling offer, grid and page size dialog, note that sync is
GitHub-only, and replace the stale open item with the real ones.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GaoZtJQZwLXkEgWs8twCia

README.md

@@ -23,7 +23,8 @@ The image builds the PWA and serves it with nginx. Put an HTTPS reverse proxy in
 ## Using it
 
 - **Tools** (bottom bar): Text `T`, Pen `P`, Highlighter `H`, Eraser `E`, Import PDF, Undo/Redo, zoom. The pen's eraser end erases too.
-- **Pages**: the grey "+" tiles next to the active page add a page there; `Alt+Arrow` moves to (or creates) the neighbour. Right-click a page or use its `⋯` button to insert, resize or delete it.
+- **Pages**: the "+" circles beside the active page add a page there (a quick finger fling past a free edge highlights that side's "+"); `Alt+Arrow` moves to (or creates) the neighbour. Right-click a page or use its `⋯` button to insert, resize or delete it.
+- **Grid**: the faint background grid has one cell per active page; Settings → Appearance can hide it or subdivide it.
 - **Importing a PDF** into a non-empty canvas shows every free spot; click one to place the chain. Into a blank canvas it simply replaces the empty page. The Files panel can also import a PDF as a new canvas.
 - **View**: wheel/trackpad pans, `Ctrl`+wheel or pinch zooms, `Ctrl+0` fits the page, `Ctrl+9` shows the whole tree, space-drag or middle-drag pans.
 - **Sync**: Settings → Sync. Use a fine-grained token with *Contents: read & write* on the repo. Edits autosave locally; pushes happen every N minutes and on `Ctrl+S` / the sync button. Conflicts: newer wins.

spec.md

@@ -9,10 +9,11 @@ One canvas = one tree = one `.pdf` file.
   - A branch can only ever continue in the direction it started (strictly linear — no sub-branches off a branch).
   - A trunk page can have at most one left branch and one right branch.
 - **PDF import**: creates a chain of pages in whatever direction you pick when placing it (up/down = extends the trunk, left/right = becomes a branch off the trunk page you clicked). Only one trunk exists per canvas — additional imported PDFs must attach as a branch off some trunk page, or extend an existing branch further outward in its established direction.
-- Hidden/unopened neighbor pages render as a gray tile with a "+" in a circle; clicking (or a shortcut) instantiates them as real pages.
+- Each free side of the active page shows a small "+" circle just off its edge; tapping it (or `Alt+Arrow`) adds a blank page there. A quick finger fling past a free edge highlights that side's "+" for a few seconds, but never adds a page by itself.
+- The canvas background is a faint grid with one cell per active page, aligned to its edges; Settings can hide it or subdivide it.
 - Deleting a page removes it (undo via Ctrl+Z); no permanent trash.
 - Default zoom: one page fills the screen. Zoom out reveals the tree.
-- Pages default to A4, or auto-match the aspect ratio of an imported PDF page; resizable manually otherwise.
+- Pages default to A4, or auto-match the aspect ratio of an imported PDF page; resizable manually otherwise (page menu: presets, or a custom size in mm).
 
 ## 2. Flatten Algorithm (tree → linear page order, e.g. for PDF page order / print)
 
@@ -45,7 +46,7 @@ Canvases (PDF files) live in a **file tree** you define, e.g. `school/english/le
 
 ## 5. Sync & Storage
 
-- Repo-backed (GitHub/GitLab), one file per canvas.
+- Repo-backed (GitHub for now; GitLab not implemented), one file per canvas.
 - PWA: offline-first, caches locally, explicit save/sync pushes to repo.
 - Multi-device: git pull/push is the sync mechanism (not real-time collab).
 
@@ -54,7 +55,7 @@ Canvases (PDF files) live in a **file tree** you define, e.g. `school/english/le
 - **Frontend**: SvelteKit, deployed on your VPS, installable as PWA.
 - **Ink input**: Pointer Events + pressure (your existing artifact — pending).
 - **PDF read/write**: pdf.js + pdf-lib.
-- **Storage**: Git repo via GitHub/GitLab API (or local backend proxy holding the token).
+- **Storage**: IndexedDB locally; Git repo via the GitHub REST API (token in the browser, no proxy).
 
 ## 7. Confirmed Product Features
 
@@ -79,12 +80,23 @@ Source: user-provided `palm-rejection-test.html` test harness. The acceptance po
 - A `touch` pointer is rejected if any of: a pen stroke is active or was active within the last ~5s, its contact ellipse (`width`/`height`) exceeds ~35px (palm heel vs. fingertip), it's within 150ms of the last pen activity, or a pen is currently hovering (armed lockout before it even touches down).
 - A touch stroke already in progress gets cut off mid-stroke if pen activity appears.
 
-**Gaps before this is the real ink engine** (currently a raster test, not vector):
-- `draw()` writes straight to canvas via `ctx.lineTo`/`stroke` with pressure-scaled line width, and throws points away. Needs to become `recordPoint()`: push `{x, y, pressure, tiltX, tiltY, t}` into a `Stroke.points[]` array per stroke; rendering = replaying that array. This is what makes strokes resizable/erasable/undoable and exportable to both the PDF Ink-annotation layer and the JSON attachment layer.
-- `tiltX`/`tiltY` exist on the pen's `PointerEvent` but aren't read anywhere yet — needed for tilt support.
-- No smoothing yet (raw straight segments) — fine as a v1, can layer in curve smoothing later without changing point storage.
-- No undo/redo, multi-color, eraser yet — needs a `Stroke[]` array per page's ink layer with add/remove, which undo/redo just pops/pushes.
+**How the app applies it** (`src/lib/ink/palm.ts`):
+- Each touch is evaluated with an intent. `draw` (finger ink) gets the full policy above. `navigate` (pan, pinch, and taps on canvas buttons such as the add-page "+") skips the 5 s pen session and the hover lockout, so fingers can move around and tap between pen strokes; pen-down, wide contacts and the 150 ms window still reject it.
+- Once a pen has been used, fingers only navigate. "Draw with finger" in Settings turns finger ink off entirely.
+- Each rule (pen session, wide contact, timing, hover) can be switched off in Settings → Pen & touch.
+- An interrupted pointer (`pointercancel`) drops the stroke or erase in progress instead of committing it.
+
+**Ink engine (implemented)**:
+- `StrokeRecorder.recordPoint()` stores `x, y, pressure, tiltX, tiltY, t` per sample in a flat `Stroke.points` array (stride 6); rendering replays it. Tilt is recorded but not yet used for rendering.
+- Outlines are smoothed with `perfect-freehand`; mouse and finger strokes simulate pressure.
+- Pen, highlighter (translucent, no thinning) and stroke eraser, with configurable colour palettes; the pen's eraser end erases too.
+- Undo/redo covers ink, erasing and page-tree changes.
+- Strokes are written to the PDF both as Ink annotations and as JSON attachments.
 
 ## 10. Open Items
 
-- [ ] Nothing blocking — ready to move into implementation planning (component breakdown, page-tree data structures in Svelte, PDF encode/decode module)
+- [ ] Conflict copies: sync currently lets the newer version win silently; keep the losing version as a separate file.
+- [ ] Tell the user when a new version of the app has been deployed (the service worker updates, but the open tab keeps old code until reload).
+- [ ] CI that runs `check`, `test` and `build` on every pull request.
+- [ ] Use recorded tilt for rendering.
+- [ ] GitLab sync.