M8: Flock Splits — first open-ended mini-game

[season179]

Work mode: AFK — carry through to merge + deploy per acceptance criteria.

The first real-mechanic experiment (not a quiz wrapper): a corral in Woolly
Meadows where the child partitions 10 fluffballs between two pens any way
they like. Every non-empty split is accepted; the delight is discovering
distinct decompositions (6 + 4 = 10), not being judged. Session-local
only: no save changes, no journal, no variant reward, no question banks, no
generic activity framework, no new art assets.

Design context: meadow-isle.md §2 (ten-pen fences, number bonds) and the
reserved mini-game pocket concept. This module is deliberately not an
answer_form precedent — the first-class activity-form question in
meadow-isle.md stays open.

Touch set (exact)

• shared/telemetry.ts — add minigame_session_ended event spec (below).
• game/assets/shared/telemetry.ts — synced copy via npm run sync.
• game/assets/src/world/flock-splits.ts — NEW pure rule module (no cc
  imports): split canonicalization, move/submit rules, session state,
  entry-critter placement.
• game/assets/src/world/FlockSplitsScreen.ts — NEW screen (cocos).
• game/assets/src/world/arc.ts — extend ArcCritter.kind union with
  "minigame" (one line; nothing else changes).
• game/assets/src/world/WorldScreen.ts — route bump/interact on
  kind === "minigame" critters to actions.onMinigame(critter); combine
  flockSplitsCrittersFor(regionId) into the existing critter render pass.
• game/assets/src/GameApp.ts — Screen union + startMinigame /
  endMinigame (ShopScreen pattern); emit telemetry once on teardown.
• game/tests/flock-splits.test.ts — NEW pure tests.
• docs/preview-smoke-check.md — add the mini-game smoke steps.
• New-file .metas generated by the Cocos build, committed (existing
  pattern).

shared/question-v2.ts, question banks, save-v2, persistence, worker
source: untouched.

Data / control flow

1. flockSplitsCrittersFor("meadow/woolly") returns one entry critter
   (kind: "minigame", speciesId woolly/fluffball, walkable tile pinned
   by test — suggested x=8, y=6 in the north pen interior).
2. WorldScreen bump/interact → WorldActions.onMinigame →
   GameApp.startMinigame() mounts FlockSplitsScreen.
3. Screen holds session state from the pure module:
   { staging: 10, pens: [0, 0], found: string[], rounds: 1, dupes: 0 }.
   All mutations go through the pure functions; the screen only renders.
4. Exit button or completion → GameApp.endMinigame(result) → emit
   minigame_session_ended once → destroy screen, world resumes in place.

UI states

• Playing: staging area with 10 fluffball placeholder nodes; two pen
  zones. Tap a pen to arm it (highlighted); tap a sheep in staging to send
  it to the armed pen; tap a sheep in a pen to return it to staging. Each
  pen shows a live count numeral + ten-frame (paintCellGrid, existing
  FigureView painter). A bilingual confirm button ("好了!/Done") submits.
• Split feedback (submit):
  • staging not empty → gentle nudge ("还有羊在外面"), no state change;
  • a pen is empty → gentle nudge ("两个围栏都要有羊哦");
  • duplicate (canonical key already found, e.g. 4+6 after 6+4) → gentle
    "这种分法找过了", dupes++, sheep stay put;
  • accepted → the equation card shows (6 + 4 = 10), sheep settle,
    found records the key, next round resets pens to staging.
• Complete (3 distinct): the session's equation cards shown together,
  celebratory bilingual line, Replay (resets found, rounds++) and
  Exit buttons.
• No timer anywhere; failure states are impossible by construction.

Pure module API (contract for tests)

[season179]

AFK release completed. PR #89 merged as 6ccdaa9; worker registry deployed first (1b0165e3-dd1b-41e3-9f88-cd5b8c838a6b), then the merged client/worker deployed as 5f78b0ba-8658-46b8-9717-e1da6e9759a9. Final gates: 561 tests, typecheck, metas, Cocos build (exit 36), and the full Harbor↔Meadow agent-browser smoke check passed with clean console/errors and one valid minigame_session_ended event. Review-discovered smoke-doc drift was corrected separately in #90 / PR #91.