feat(runtime): scheduler-via-runSkill + Pi banter escalation + base-site (follow-ups) (#20)

Three closures of remaining PRD follow-ups, one merge:

1. Reflex scheduler now drives behaviour from the curriculum.
   - reflex.js: replaced ad-hoc techTreeReflex + autonomousReflex with
     curriculumReflex that dispatches the skill suggested by
     snapshot.curriculum.plan via runSkill. Per-skill backoff for
     missing_tool / missing_material / no_target / no_food_source /
     unsupported_version. recover() hint with `{hint:"wander"}` swaps
     the next tick to wander for 60 s.
   - Chain is now: defend > eat > sleep > curriculum > idle.
   - reflex.test.js: 11 new tests covering busy/disconnected,
     defend/eat preemption, dispatch by id, unknown-skill fallback,
     per-skill + wander-hint backoffs, onComplete updating backoff.

2. Pi escalation for ADDRESSED_BANTER with hard rate limit.
   - bot.js: when generateReply returns {escalate:true}, spawn askPi
     with bot state + last 5 lines from that speaker (redacted via
     chatMemory). Reply capped at 200 chars, sent as one chat line.
   - Rate cap: 6 calls/hour, 90 s min gap. Suppressed escalations
     log once and silently drop.

3. Phase 4 substrate.
   - runtime/locations.js: atomic JSON store
     (state/<host>/locations.json) with setLocation / getLocation /
     nearestLocation / removeLocation; 6 tests.
   - runtime/base-site.js: scoreCurrentPosition(bot) + pure scoreSite
     bundle (wood / stone / water / flatness / no-players /
     no-foreign-builds, owned-blocks excluded from claim penalty);
     6 tests.
   - runtime/skills/choose-base.js: village.choose-base skill — scores
     the current spot, writes locations.base if score ≥ 8, otherwise
     returns code:"too_weak" with a wander recover hint.
   - curriculum.js: new final milestone village.base-site fires
     village.choose-base until a base location exists.
   - bot.js: stamps snapshot.locations from listLocations() each tick
     so the curriculum can read it without coupling to disk.

docs/runtime.md updated with three new sections.
npm test now 116/116.

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

runtime/curriculum.js

@@ -130,6 +130,16 @@ const MILESTONES = [
 		isDone: (inv) => has(inv, "torch", 4),
 		suggest: () => ({ skillId: "craft.torch" }),
 	},
+	{
+		id: "village.base-site",
+		title: "Pick a base site",
+		// We treat this as done when a "base" location exists in
+		// locations.json. The curriculum can't read that file from here
+		// (would couple it to disk), so we expose a snapshot hint:
+		// `snapshot.locations?.base` is filled by bot.js.
+		isDone: (_inv, snap) => !!snap?.locations?.base,
+		suggest: () => ({ skillId: "village.choose-base" }),
+	},
 ];
 
 export function isInventoryFull(snapshot) {