[FEATURE] Gamepad, action contexts, input feel helpers, local player slots and split-screen viewports

[Noisemaker111]

Problem: no gamepad, no input contexts, no input buffering, no local players. Verified on main: zero hits for getGamepads and unadjustedMovement in packages/; packages/core/src/game/controlGate.ts is one boolean; packages/core/src/runtime/inputSnapshot.ts is one global held set; CameraKind = "splitScreen" in packages/core/src/visibility/camera.ts is unused.

Tasks, one PR each, in order:

1. Gamepad model (core). New packages/core/src/input/gamepadModel.ts: GamepadSnapshot { id: string; axes: number[]; buttons: { pressed: boolean; value: number }[]; connected: boolean }, GamepadBindings mapping action names to pad:<buttonIndex> and padaxis:<axisIndex>[+-] codes (extend ActionBinding code parsing in packages/core/src/input/actionBindings.ts to accept these strings), resolveGamepadFrame(snapshot, bindings, { deadzone: { kind: "radial" | "axial"; inner: number; outer: number }; curve?: number }) -> { held: string[]; analog: Record<string, number> }. GamepadGlyphSet data for xbox, playstation, nintendo, generic and bindingLabel returns the glyph text for pad codes. Tests: deadzone, curve, glyphs. bun run gen. CHANGELOG Added.

2. Gamepad source (shell). New packages/shell/src/input/gamepadSource.ts: polls navigator.getGamepads() in useFrame, merges the resolved frame into the tracker/analog refs FrameDriver reads, and exposes rumble(userId, { strong, weak, ms }) on ctx.input via vibrationActuator.playEffect. Mount it in GamePlayerShell.tsx. Since Playwright cannot attach a pad, add a synthetic GamepadSnapshot injector (?gamepad=1 dev overlay) and a test on the pure merge.

3. Action contexts. New packages/core/src/input/actionContexts.ts: createActionContextStack() with push({ id; codes: ActionCodesMap; passthrough: boolean }), pop(id), active() -> ActionCodesMap (merged top-down until a non-passthrough), snapshot, restore. Replace the boolean in controlGate.ts with a menu context push, keeping playControlsActive as a wrapper. Wire the tracker in packages/shell/src/input/ to read active(). Tests.

4. Input feel helpers. New packages/core/src/input/inputBuffer.ts: createInputBuffer({ windowMs }) with press(action, nowMs), consume(action, nowMs) -> boolean, coyote(groundedAtMs, nowMs, windowMs) -> boolean, hold(action, nowMs) -> ms held, doubleTap(action, nowMs, gapMs), snapshot/restore. Consume it in packages/core/src/movement/playerMovement.ts for jump (buffered jump and coyote time behind movement.jumpBufferMs / coyoteMs, default 0 so behavior is unchanged). Tests.

5. Raw mouse. In packages/shell/src/input/mouseLook.ts request requestPointerLock({ unadjustedMovement: true }) with a fallback to the plain call when the promise rejects.

6. Local player slots. New packages/core/src/runtime/localPlayers.ts: createLocalPlayers({ maxSlots }) with assign(deviceId) -> slotId (hot-join on first input), slots(), one InputSnapshot per slot, snapshot/restore. ctx.player stays the primary; add ctx.players.local(slotId) returning { userId; input }. The game loop spawns one entity per slot through onNewPlayer. Tests.

7. Split-screen viewports. New packages/core/src/game/viewports.ts: ViewportDef { slot: string; rect: [x, y, w, h] (0..1); camera: GameCameraConfig }; packages/shell/src/camera/Viewports.tsx renders each viewport with gl.setViewport/setScissor in a useFrame at render priority, one camera rig per slot following that slot's entity, and a HUD root per viewport. Add viewports?: ViewportDef[] to the presentation config. Shots of two viewports.

8. Probe. Two-pad couch example under examples/ with hot-join. Closes #1686.

Rules: wait for bun run agent:bootstrap --check; branch claude/<slug> off origin/main; claim comment first; one task per PR with Refs #1686; bun run gen after export changes (JSDoc on every export; create* factories need snapshot/restore); CHANGELOG bullet; check-types and test on core, shell, react as touched plus check-stateful-ratchet, check-doc-symbols, check-orphan-ratchet; merge origin/main before pushing; shots via bun run shoot; squash auto-merge; fix CI on the same branch.

[Noisemaker111]

Claiming Task 3 (action contexts) in the Luna worktree. I’ll implement the core stack, control-gate integration, shell tracker wiring, tests, and generated artifacts. Refs #1686