feat(runtime): social layer — intent / templates / chat memory (Phase 5) (#16)

Phase 5 of plans/autonomous-survival-bot-prd.md. Make the bot feel
present in chat without ever becoming a command executor.

New: runtime/social/
- intent.js: classifyIntent({text, botName}) returns one of GREETING /
  STATUS_QUESTION / ADDRESSED_BANTER / COMMAND_LIKE / UNSAFE_REQUEST /
  AMBIENT. Unicode-aware word boundaries so cyrillic + latin both work
  ("Привет всем" → GREETING, "build me a tower" → AMBIENT unless
  addressed).
- reply.js: generateReply({intent, speaker, snapshot, diaryTail}) →
  short templated response, or {send: null, escalate: true} for the
  caller to decide whether to spend Pi tokens.
- memory.js: createChatMemory() — per-speaker LRU buffer of recent
  lines; redacts password / api_key / JWT-shaped tokens at append
  time, so the buffer can be safely fed back into any future prompt.
- social.test.js: 12 tests (intent edges, memory eviction, redaction,
  reply routing). npm test now 40/40.

state-store.js additions:
- readDiaryTail(n) — reads the last N lines of today's diary; used by
  status replies.
- writeEscalation({from, request, whyUnsure, wouldHave}) /
  listEscalations() — JSONL log under state/<host>/escalations.jsonl
  for UNSAFE_REQUEST classifications and future operator review.

bot.js: handleChat() now routes through social/intent + social/reply
(replacing the Phase-0 inline regexes), records every line into
chatMemory, and writes an escalation when classifyIntent returns
UNSAFE_REQUEST. Command-like notice + dialog-only behaviour from
Phase 0 are preserved.

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

docs/runtime.md

@@ -246,6 +246,31 @@ in-process. The package is **not** a default dep — install it explicitly
 (`npm i prismarine-viewer`) before enabling. If missing, the runtime
 logs a warning and continues.
 
+### Social layer (Phase 5)
+
+Inbound MC chat is classified via `runtime/social/intent.js` into one
+of `GREETING` / `STATUS_QUESTION` / `ADDRESSED_BANTER` / `COMMAND_LIKE`
+/ `UNSAFE_REQUEST` / `AMBIENT`. The classifier uses Unicode-aware
+boundaries so "Привет всем" lands as `GREETING` while
+"build me a tower" stays `AMBIENT` until the bot is addressed.
+
+`runtime/social/reply.js` turns an intent into a short reply:
+- `GREETING` → one of a small picked-randomly set ("yo" / "привет" / …).
+- `STATUS_QUESTION` → live snapshot summary: active skill, current
+  milestone, hp/food/position, no-progress reason, last diary line.
+- `COMMAND_LIKE` → dialog-only notice (per Phase 0).
+- `UNSAFE_REQUEST` → terse "logged for operator review", plus an entry
+  in `state/<host>/escalations.jsonl`.
+- `ADDRESSED_BANTER` → templates can't reliably answer, so the
+  generator returns `escalate: true`. Today bot.js does NOT spawn Pi
+  from this path (keeps the LLM out of the hot path); a rate-limited
+  escalation lands in Phase 6.
+
+`runtime/social/memory.js` maintains an LRU per-speaker buffer of
+recent lines (default 8 per speaker, 16 speakers max) and redacts
+password / api-key / JWT-shaped tokens before they ever exit the
+runtime.
+
 ## In-game chat (dialog-only)
 
 As of the Phase 0 survival-bot pivot, MC chat does **not** drive bot