feat(runtime): observability + no-progress detector (Phase 1) (#13)

Phase 1 of plans/autonomous-survival-bot-prd.md. The bot must always be
able to answer "what am I doing and why am I not doing more?" without
parsing the log stream.

New modules:
- runtime/state.js: pure FSM classifier emitting emergency / working /
  recovering / planning / social / idle from snapshot + reflex context.
- runtime/no-progress.js: sliding-window detector that watches position
  and inventory; when both are unchanged for 60 s+, emits one stable
  reason code from REASONS (waiting_for_day, night_hostile_nearby,
  no_food_source, inventory_full, no_reachable_target, planner_empty,
  awaiting_action_cooldown).
- runtime/viewer.js: optional prismarine-viewer launcher behind
  VIEWER_PORT. Lazy import so the dep is not required by default.

Wiring:
- runtime/bot.js: tick() now computes runtimeState + noProgressReason
  every tick and stamps them on the snapshot along with activeSkill,
  currentMilestone (read from plan.md, cached 30 s), lastResult,
  failuresByCode and lastEscalation.
- runtime/bot.js: dispatchAction records lastResult and lastFailureAt
  for the recovering-state classifier.
- runtime/planner.js: exports isPlannerBusy(), readNextMilestone()
  and planExists() so the runtime can show planning state + current
  milestone without spawning extra Pi calls.
- runtime/config.js: adds VIEWER_PORT support.

TUI:
- tui/tui.tsx: StatusBar gains a state badge, current-skill row,
  milestone row, no-progress reason warning, last-result line with
  ok/fail color, failures-by-class summary and last-escalation age.

Co-authored-by: Yuriy Mayatnikov <mayatnikov@me.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

runtime/config.js

@@ -44,6 +44,11 @@ export const config = Object.freeze({
 		.filter(Boolean),
 	tickIntervalMs: Math.max(1, Number.parseInt(opt("TICK_INTERVAL_SECONDS", "3"), 10)) * 1000,
 	chatRateLimitPerMin: Number.parseInt(opt("CHAT_RATE_LIMIT_PER_MIN", "15"), 10),
+	// Optional prismarine-viewer port for local visual debugging. 0/empty = off.
+	viewerPort: (() => {
+		const v = Number.parseInt(opt("VIEWER_PORT", "0"), 10);
+		return Number.isFinite(v) && v > 0 ? v : 0;
+	})(),
 });
 
 export const serverKey = `${host}_${port}`;