feat(tiles): Tile Animations setting, entrance styles for the tile grid

Tiles become the fifth entrance surface (data-tile-anim), switched on in App
Settings > Appearance > Tile Animations and OFF by default: the default is the
grid's own quick fade (`settle`), exactly as before.

A styled tile plays in two beats: its frame enters as it mounts (fly out of
its session tab, dealt from the Tiles button, CRT power-on, beam down from its
tab, cascade, pop, soft), and its screen then plays the terminal pane style of
the entrance theme when its first capture lands, through the same
html[data-term-anim] rules on .tile-body. Each style has its own exit when the
Tiles button closes the grid (back into the tabs, a CRT switch-off, ...).

Picking an Entrance Animations theme presets the tile style (new Launch theme:
tiles fly from the tabs); the theme readout ignores the tile row, so changing
it never shows "Custom". Frames move transform and opacity only (one fit and
one PTY resize per tile), a reload's restore always settles, and nothing moves
under reduced motion. The lab (?animlab=1) gets a Tile grid group, a cascade
order picker and in-place replay / close + reopen.

Also removes the terminal pane's `boot` entrance style (owner decision); a
saved `boot` falls back to off.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -877,7 +877,7 @@ Tests: `test/terminal-touch-tap.test.ts`.
 
 ### Entrance animations
 
-**Entrance animations** (`entrance-animations.js`, all OFF by default): opt-in animations for the four things that appear when work starts, chosen per surface via `data-tab-anim` / `data-term-anim` / `data-win-anim` / `data-line-anim` on `<html>`. Defaults are the `legacy` theme, so an untouched install behaves exactly as before and every hook short-circuits on its first line. Persisted to its own `codeman:*Anim` localStorage keys (per-device, deliberately NOT in the `.strict()` `SettingsUpdateSchema`); picker in App Settings → Appearance, full per-surface lab at `?animlab=1`.
+**Entrance animations** (`entrance-animations.js`, all OFF by default): opt-in animations for the five things that appear when work starts, chosen per surface via `data-tab-anim` / `data-term-anim` / `data-win-anim` / `data-line-anim` / `data-tile-anim` on `<html>`. Defaults are the `legacy` theme, so an untouched install behaves exactly as before and every hook short-circuits on its first line. Persisted to its own `codeman:*Anim` localStorage keys (per-device, deliberately NOT in the `.strict()` `SettingsUpdateSchema`); picker in App Settings → Appearance, full per-surface lab at `?animlab=1`.
 
 ⚠️ Tabs and connection lines are **destroyed mid-animation** on every re-render (`_fullRenderSessionTabs()` replaces the strip's innerHTML; `_updateConnectionLinesImmediate()` does `svg.innerHTML = ''`), so both are tracked by id and re-applied to the fresh element with a **negative `animation-delay`** to resume rather than restart.
 
@@ -889,6 +889,14 @@ Tests: `test/terminal-touch-tap.test.ts`.
 
 ⚠️ Window styles other than `beam` transform the window, which moves the rect its connection line is aimed at; `beam` deliberately animates opacity/filter only so its line can draw toward a stable target.
 
+**Tile grid entrances (the fifth surface, `data-tile-anim`).** A tile plays in two beats: its FRAME enters as it mounts in a `TILE_ANIM_STYLES` style (`settle`, `fly`, `deal`, `crt`, `beam`, `cascade`, `pop`, `soft`, `off`), and its SCREEN (`.tile-body`) plays the terminal pane's style when the load queue reports its first capture, through the same `html[data-term-anim]` rules (each names `.terminal-container.term-enter` AND `.tile-body.term-enter`). Content that lands while the frame is still entering waits for it (`--tile-screen-delay`), and the screen's `::before` wash fills `forwards` only, so a held wash never shows as a bright static block. Tiles are OFF by default: the style is its own setting, App Settings → Appearance → **Tile Animations** (`#appSettingsTileAnim`, `codeman:tileAnim`), whose default `settle` is the grid's own fade and settle (`.tile--entering`, pinned by `test/tile-grid-motion.test.ts`) with no screen beat and the plain exit, exactly as before. No saved key means `settle`, so a theme saved before tiles existed gives them nothing new. Picking a theme PRESETS the tile style (every theme carries a `tile` key, `legacy` → `settle`), but the theme readout (`currentAnimTheme`) is matched on the four classic surfaces only, so changing the tile row afterwards never turns the theme into "Custom". The screen beat plays only for a tile style other than `settle`.
+
+⚠️ Tile FRAME keyframes animate **transform and opacity only**, colour on a `::before` wash: six tiles animate at once, so no `filter` (a tile's blur is its screen beat, one tile at a time as the queue serves captures). The keyframes are named `tile-enter*` / `tile-leave*` because that is what the mount's `animationend` and the still copy's removal listen for, ignoring any event with a `pseudoElement`. `test/entrance-animations.test.ts` pins both.
+
+⚠️ A themed tile is held one frame (`.tile--enter-hold`: invisible, `animation: none`), then `_runTileEntrances` orders the cascade from the final cells (`reading` / `wave` / `ripple`, a lab override in `codeman:tileAnimOrder`) and, for `fly`/`deal`/`beam`, measures its source (its session tab, else the Tiles button) on the final layout: `openTileGrid` packs tiles and a stored grid then moves them back, so measuring at mount would aim at the wrong cell. The offset rides `--tile-from-*` custom properties set BEFORE the hold comes off. The mount arms a backstop (4 s at once, the precise one from the module), so a frame that never comes cannot strand a tile invisible.
+
+⚠️ **A reload's restore always settles** (`_tileEnterQuiet` around `_restoreTileGrid`) and owes no screen beat: nothing animates on page load. A re-form (count change) keeps the plain fade on its still copy (`--now`), because that copy covers tiles that stay; only the Tiles toggle's close plays the style's own exit (`_stageTileExit`: back into the tabs, a CRT switch-off), and the copy's fallback timer waits as long as that exit says.
+
 ### Mobile tab strip scrolling
 
 **Mobile tab strip scrolling** (issue #257): under 768px the tab strip is a horizontal scroller (desktop wraps to a second row instead), so the active tab can sit off-screen. Three rules keep it reachable and they only work together: `_updateActiveTabImmediate()` scrolls the selected tab into view via `computeTabScrollLeft()` (pure, in constants.js) using **rect math on the strip's own `scrollLeft`**, never `scrollIntoView()`, which would also scroll the document under a fixed header; `_fullRenderSessionTabs()` **restores `scrollLeft`** across the `innerHTML` rebuild, since ambient rebuilds (a task badge appearing, a session created elsewhere) otherwise snap a mid-swipe strip back to 0; and it re-reveals the active tab **only when it changed** (`_lastRenderedActiveTabId`), so browsing the far end of the strip is not undone by background renders.