feat(settings): an Animations section in App Settings

Every animation setting now has its own App Settings section, right after
Appearance (owner: easier to find). It holds the Entrance Theme (the former
Entrance Animations row), Tile Animations, and an Open lab button that closes
settings and opens the per-surface lab (?animlab=1). Appearance keeps the skin,
identity and tab settings. New animation settings go in this section;
test/app-settings-structure.test.ts pins it.

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 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`.
+**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 its own App Settings → **Animations** section (`#settings-animations`: the Entrance Theme, Tile Animations, and an Open lab button), full per-surface lab at `?animlab=1`. New animation settings go in that section.
 
 ⚠️ 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.
 
@@ -889,7 +889,7 @@ 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 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 → Animations → **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.