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/state.js

@@ -0,0 +1,57 @@
+// Finite-state classifier for the runtime. Each tick the bot is in exactly
+// one of:
+//
+//   emergency  — survival is at risk (low HP, hostile in melee, drowning…)
+//   working    — an async action is in flight (reflexCtx.busy === true)
+//   recovering — last action failed recently and we are in its cooldown
+//   planning   — the LLM planner is computing a fresh plan.md
+//   social     — we just produced a chat reply (cools down social activity)
+//   idle       — none of the above; the bot is up but nothing is happening
+//
+// Pure function: takes the current observed inputs and returns a string.
+// No side effects; the caller decides what to do with the classification.
+
+export const STATES = Object.freeze({
+	EMERGENCY: "emergency",
+	WORKING: "working",
+	RECOVERING: "recovering",
+	PLANNING: "planning",
+	SOCIAL: "social",
+	IDLE: "idle",
+});
+
+const EMERGENCY_HP = 8;
+const EMERGENCY_HOSTILE_DISTANCE = 4;
+const RECOVERING_WINDOW_MS = 30_000;
+const SOCIAL_WINDOW_MS = 5_000;
+
+export function computeState({
+	snapshot,
+	ctx,
+	plannerInFlight = false,
+	lastChatReplyAt = 0,
+	lastFailureAt = 0,
+	now = Date.now(),
+}) {
+	if (!snapshot?.connected) return STATES.IDLE;
+
+	const hp = snapshot.health ?? 20;
+	if (hp <= EMERGENCY_HP) return STATES.EMERGENCY;
+	if (snapshot.closestHostile && snapshot.closestHostile.distance <= EMERGENCY_HOSTILE_DISTANCE) {
+		return STATES.EMERGENCY;
+	}
+
+	if (ctx?.busy) return STATES.WORKING;
+
+	if (lastFailureAt && now - lastFailureAt < RECOVERING_WINDOW_MS) {
+		return STATES.RECOVERING;
+	}
+
+	if (plannerInFlight) return STATES.PLANNING;
+
+	if (lastChatReplyAt && now - lastChatReplyAt < SOCIAL_WINDOW_MS) {
+		return STATES.SOCIAL;
+	}
+
+	return STATES.IDLE;
+}