feat: vendor gesture-control source into packages/gesture-control

Bring the Ark0N/codeman-gesture-control repo in-tree as the codeman-gesture-control
workspace package so the hand-tracking overlay can be developed in the Codeman repo.
New npm run build:gesture bundles src/codeman/entry.ts into the served
gesture-codeman.js; scripts/build.mjs reruns it on every production build.
Source formatted to Codeman's prettier style.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/gesture-control/src/gesture/commands.ts

@@ -0,0 +1,78 @@
+// Discrete gesture → command detection.
+//
+// Maps the recognizer's canned gesture categories onto Codeman commands, with
+// debouncing so each command fires once per gesture *entry* (not every frame
+// while it's held). Open_Palm is special: it must be held continuously for
+// `palmHoldMs` before firing halt-all — a dead-man's-switch that's hard to
+// trigger by accident, since pausing every session is a big hammer.
+
+import type { CommandName } from './types.ts';
+
+interface CommandSpec {
+  name: CommandName;
+  /** If set, the gesture must be held this long (ms) before it fires. */
+  holdMs?: number;
+}
+
+/** MediaPipe canned gesture category → command. */
+const GESTURE_COMMANDS: Record<string, CommandSpec> = {
+  Open_Palm: { name: 'halt-all', holdMs: -1 }, // holdMs filled from palmHoldMs
+  Thumb_Up: { name: 'approve' },
+  Victory: { name: 'new-session' },
+};
+
+export class CommandDetector {
+  /** gesture category → timestamp (ms) it was first seen in the current hold. */
+  private heldSince = new Map<string, number>();
+  /** gestures that already fired during the current hold (cleared on release). */
+  private fired = new Set<string>();
+
+  constructor(private palmHoldMs = 1000) {}
+
+  reset(): void {
+    this.heldSince.clear();
+    this.fired.clear();
+  }
+
+  private holdMsFor(spec: CommandSpec): number {
+    return spec.holdMs === -1 ? this.palmHoldMs : (spec.holdMs ?? 0);
+  }
+
+  /**
+   * Feed the set of command-gestures currently shown (across all hands).
+   * @returns the commands that fired on this frame (usually empty).
+   */
+  update(gestures: Set<string>, nowMs: number): CommandName[] {
+    // Forget gestures no longer held, so they can re-fire on the next entry.
+    for (const g of [...this.heldSince.keys()]) {
+      if (!gestures.has(g)) {
+        this.heldSince.delete(g);
+        this.fired.delete(g);
+      }
+    }
+
+    const fired: CommandName[] = [];
+    for (const g of gestures) {
+      const spec = GESTURE_COMMANDS[g];
+      if (!spec) continue;
+
+      const since = this.heldSince.get(g) ?? nowMs;
+      if (!this.heldSince.has(g)) this.heldSince.set(g, since);
+      if (this.fired.has(g)) continue;
+
+      if (nowMs - since >= this.holdMsFor(spec)) {
+        fired.push(spec.name);
+        this.fired.add(g);
+      }
+    }
+    return fired;
+  }
+
+  /** 0–1 charge of the held halt-all gesture (1 once fired, 0 when released). */
+  haltProgress(nowMs: number): number {
+    const since = this.heldSince.get('Open_Palm');
+    if (since === undefined) return 0;
+    if (this.fired.has('Open_Palm')) return 1;
+    return Math.min(1, (nowMs - since) / this.palmHoldMs);
+  }
+}