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

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: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

runtime/viewer.js

@@ -0,0 +1,30 @@
+// Optional prismarine-viewer launch — local visual debugging surface.
+// Activated by setting VIEWER_PORT in .env (e.g. 3007). The dependency is
+// not required at runtime: if `prismarine-viewer` is not installed, this
+// module logs once and returns, so production deploys aren't forced to
+// carry the extra dep.
+
+import { info, warn } from "./log.js";
+import { config } from "./config.js";
+
+let started = false;
+
+export async function maybeStartViewer(bot) {
+	if (started) return;
+	const port = config.viewerPort;
+	if (!port) return;
+	let mineflayerViewer;
+	try {
+		({ mineflayer: mineflayerViewer } = await import("prismarine-viewer"));
+	} catch (e) {
+		warn("viewer", `VIEWER_PORT=${port} requested but prismarine-viewer is not installed (npm i prismarine-viewer)`);
+		return;
+	}
+	try {
+		mineflayerViewer(bot, { port, firstPerson: false });
+		started = true;
+		info("viewer", `prismarine-viewer listening on http://localhost:${port}`);
+	} catch (e) {
+		warn("viewer", `failed to start: ${e?.message ?? e}`);
+	}
+}