feat(web): desktop mascot ("Cluck") — egg/chick/adult tamagotchi that roams the desktop, reacts to chat/events, walks on top of windows

Implements plans/2026-07-20-desktop-mascot.md. New code under
web/src/lib/mascot/ (types/sprites/render/state/behavior/actions/
stimuli + Mascot/MascotLayer/RadialMenu/NameDialog components) plus
CC0 sprite sheets at web/public/mascot/ (chicken + Onocentaur egg pack
+ reaction bubbles). MascotLayer is inserted into Desktop.svelte after
WindowLayer; <2-line integration.

Tamagotchi: egg -> chick -> adult lifecycle persisted to
localStorage['oikos-mascot'] (debounced 300ms). Egg hatches on first
naming (no timed incubation per implementation deviation). Chick/adult
wander, peck, sleep, blink autonomously via a weighted-random FSM; the
chicken walks above windows (ground line = highest window top edge
beneath its x, recomputed each tick from wmState; rides the ground when
the window beneath is dragged).

Interaction: draggable with flutter-fall physics on release mid-air;
plain click = pet (heart bubble + happy anim); right-click opens a
rounded-button radial menu (Interact/Care/Identity/Debug nested groups)
mirroring the desktop's own right-click menu styling; auto-flips above/
left near screen edges.

Awareness: stimulus bus subscribes to chat.ts streaming, activity.ts
activityLog (knowledge-entry diff), events.ts liveEvents (critical/
signal -> alarmed, execution -> happy), with priority+cooldown gating.
Egg-stage reactions are suppressed. Reaction bubbles are anti-aliased.

Sprite loop runs at ~60fps via setTimeout (not rAF) per GraphBackground
convention, dt clamped to 100ms; position via transform: translate3d
+ will-change: transform for compositor-friendly motion. Z-index
ordering: WindowLayer z-40 < MascotLayer z-[45] < desktop context menu
z-50 < RadialMenu/NameDialog z-[60].

Docs: plan + docs/mascot/README.md (MBSE subsystem model) updated to
Implemented with a deviations note covering hatch-on-naming, PNG-sheet
art, button-column radial menu, 60fps loop, egg-reaction suppression,
and window-walking ground model. VERSION bumped 0.7.13 -> 0.8.0.

plans/2026-07-20-desktop-mascot.md

@@ -1,6 +1,48 @@
 # 2026-07-20 — Desktop mascot ("Cluck")
 
-**Status:** Planned
+**Status:** Implemented
+
+> **Deviations from the original plan, applied 2026-07-20 during
+> implementation:**
+> - **Hatching is no longer timed.** The egg → chick transition fires
+>   once, on first naming (the name dialog opens on first mount of a
+>   fresh egg; submitting it calls `forceHatch()`). `HATCH_MS` is gone,
+>   `tickLifecycle` no longer advances `hatchProgress`, and the egg no
+>   longer plays a progressive `egg-crack` animation — it sits on
+>   `egg-idle` until named. `hatchProgress` is retained as a binary
+>   0/1 flag so `advanceStageIfReady()` and the debug "Force hatch"
+>   action still work.
+> - **Sprite art is PNG-sheet-based, not code-drawn pixel grids.** The
+>   chicken comes from a CC0 16x16 sprite-sheet pack at
+>   `web/public/mascot/`; the egg comes from the Onocentaur egg pack
+>   (also CC0). `palette.ts` was removed; `render.ts` slices 16x16
+>   frames from sheets instead of painting string grids. Chick and
+>   adult share sheets (distinguished only by render scale) until
+>   distinct adult art is added.
+> - **The radial menu is a rounded-button column, not a circular
+>   ring.** The plan's polar-layout ring was found to hide labels; the
+>   menu now mirrors the desktop's own right-click menu styling
+>   (full-text buttons, nested via a "Back" breadcrumb).
+> - **The sprite loop runs at ~60fps** (16ms `setTimeout`), not 30fps.
+>   Drag and fall motion at 30fps looked choppy on 60Hz+ displays. The
+>   `setTimeout`-not-`rAF` convention is preserved; `dt` is still
+>   clamped to 100ms. Position is applied via `transform: translate3d`
+>   + `will-change: transform` (compositor layer) instead of CSS
+>   `left`/`top` to avoid per-frame layout reflow.
+> - **Egg-stage reactions are suppressed.** The stimulus bus still
+>   subscribes to chat/activity/events while the egg is on screen, but
+>   MascotLayer's emit callback drops any reaction when
+>   `model.stage === 'egg'` — the egg isn't "alive" yet, so playing
+>   alarm/eureka animations behind the naming dialog would be jarring.
+> - **The mascot walks on top of windows.** The ground line is
+>   recomputed each tick from `wmState`: it's the top edge of the
+>   highest non-minimized window whose horizontal span covers the
+>   mascot's x, or the surface bottom when no window is beneath. When
+>   the mascot strolls over a window, the ground rises to that
+>   window's top edge; when it walks off the side, the ground drops
+>   and it flutter-falls to the next surface beneath (another window,
+>   or the desktop). This generalizes the original "walks along the
+>   desktop surface's bottom edge" decision to a multi-surface model.
 
 ## Why
 
@@ -181,9 +223,11 @@ export function forceBehavior(rt: MascotRuntime, id: BehaviorId, opts?: { anim?:
   `weight` and are entered only via `forceBehavior()` — pointer code calls
   it for `dragged`, gravity logic for `falling`, the stimulus bus for
   `react`.
-- **Egg stage**: `behavior` locked to `'egg'` (periodic `egg-wiggle`,
-  `egg-crack` as `hatchProgress` nears 1); dragging is still allowed (the
-  egg can be picked up and moved).
+- **Egg stage**: `behavior` locked to `'egg'` (renders `egg-idle`,
+  wiggles gently via a render-time transform); dragging is still
+  allowed (the egg can be picked up and moved). The egg → chick
+  transition fires once, on first naming — see the deviation note at
+  the top of this plan.
 - Loop lives in `Mascot.svelte`: `setTimeout(() => tick(performance.now()),
   33)` inside an `$effect`, cleared on teardown, `dt` clamped to 100ms.
 
@@ -195,14 +239,13 @@ export interface MascotModel {
   version: 1
   stage: MascotStage
   name: string | null
-  hatchProgress: number       // 0..1, egg stage only
+  hatchProgress: number       // binary 0/1: 0 until first naming, 1 after (egg stage only)
   happiness: number           // 0..100, slow decay, boosted by pet/feed
   xp: number                  // chick -> adult growth hook
   hatchedAt: number | null
   lastPos: { x: number } | null
-  lastSeen: number            // for capped offline egg-incubation progress
+  lastSeen: number            // for capping passive decay
 }
-export const HATCH_MS = 3 * 60_000   // active time to hatch (demo-friendly)
 export const ADULT_XP = 200
 export function grantXp(n: number): void
 export function feed(): void
@@ -210,6 +253,7 @@ export function pet(): void
 export function setName(name: string): void
 export function tickLifecycle(dt: number): void   // called ~1x/sec, not per frame
 export function advanceStageIfReady(): void
+export function forceHatch(): void                 // called by the name-dialog submit handler on first naming
 ```
 
 - `load()` parses `localStorage['oikos-mascot']`, checks `version`, falls
@@ -220,6 +264,11 @@ export function advanceStageIfReady(): void
   debounce, plus a `beforeunload` flush so a quick reload doesn't lose a
   rename. `lastPos.x` is written only on behavior transitions and
   drag-end, never per frame.
+- The egg → chick transition is **not** timed: a fresh egg (stage=egg,
+  name=null) opens the name dialog on mount; submitting it calls
+  `forceHatch()` which sets `hatchProgress=1` and `setStage('chick')`.
+  Returning users with a named mascot skip the dialog. See the deviation
+  note at the top of this plan.
 - Multi-tab races (two tabs both writing `oikos-mascot`) are
   last-writer-wins — accepted for this scaffolding, not solved; a future
   pass could listen to the `storage` event if it becomes a real problem.
@@ -293,6 +342,12 @@ Initial wiring:
   unsubscribe into the returned teardown, so the mascot keeps the SSE
   stream open (ref-counted alongside any page that also subscribes) only
   while mounted.
+- **Egg-stage reactions are suppressed.** MascotLayer's stimulus
+  callback drops any reaction when `model.stage === 'egg'` — the egg
+  isn't "alive" yet (no name, no hatched chick to react), so stimulus
+  events are silently ignored until the egg hatches. This keeps the egg
+  calm during the naming dialog rather than playing alarm animations
+  behind it.
 - On first emission of `liveEvents`, just record the head event id — do
   not replay history as reactions on mount.
 - Dispatch: `emit(reaction)` checks the cooldown map and