fix(runtime): pin MC_VERSION=1.21.4 + ground-truth probe + close-loop dig

Two-pronged response to user-confirmed "bot stands still, doesn't actually
chop" on play.xmatic.team:

1. Pin protocol — .env now sets MC_VERSION=1.21.4. minecraft-data has
   wrong packet ID mappings for protocol 775 (server 26.1.2 via
   ViaBackwards 5.9.1) — see mineflayer#3888 and #3717. 1.21.5 also has
   an enchants decoder bug that breaks bot.dig. 1.21.4 is the last
   protocol mineflayer 4.37.1 can speak cleanly through VIA.

2. Don't trust dig success — runtime/actions.js chopNearestTree and
   runtime/skills/gather-stone.js now lookAt(face center)+forceLook,
   await collectBlock, then re-read the target block. If the log/stone
   is STILL there, return ok:false code:"silent_dig_failure" and
   blacklist the position. Prevents the curriculum from reporting
   "wood.16 in progress" while the world hasn't actually changed.

3. Defensive default — runtime/movement-profiles.js: canDig=false on
   every profile until dig is confirmed working live. Otherwise
   pathfinder schedules paths through must-dig blocks and the bot loops.

4. Ground-truth probe — runtime/skills/diagnose-physics.js dispatches
   forward/jump/dig probes and writes the result to the diary. New
   IPC command cmd:run-skill lets the operator (or a future curriculum
   trigger) fire any skill on demand; it waits for the current action
   to finish before dispatching. /tmp/pepa-runskill.mjs is a one-shot
   client.

Live probe on play.xmatic.team confirmed: forward Δ=0.003 over 2s
(BROKEN — server rejects movement packets), jump ΔY=0.42 (likely
physics jitter, not a real jump). Strongly suggests an anti-cheat
plugin gating bot-style movements server-side — beyond protocol pin.

npm test 124/124.

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

runtime/bot.js

@@ -42,6 +42,7 @@ import { createNoProgressDetector } from "./no-progress.js";
 import { maybeStartViewer } from "./viewer.js";
 import { nextMilestone as nextCurriculumMilestone } from "./curriculum.js";
 import { listLocations } from "./locations.js";
+import { runSkill } from "./skills/index.js";
 import { classifyIntent, INTENTS } from "./social/intent.js";
 import { generateReply } from "./social/reply.js";
 import { createChatMemory } from "./social/memory.js";
@@ -803,6 +804,46 @@ function handleCommand(msg, send) {
 			}
 			break;
 		}
+		case COMMAND_TYPES.RUN_SKILL: {
+			const skillId = msg.payload?.skillId;
+			const args = msg.payload?.args ?? {};
+			if (!skillId) {
+				send(EVENT_TYPES.ERROR, { source: "run-skill", text: "missing skillId" });
+				return;
+			}
+			info("ipc", `run-skill: queued ${skillId} args=${JSON.stringify(args)} (will wait for current action)`);
+			// Pause the reflex loop while we wait so it doesn't immediately
+			// schedule another action and starve our request.
+			const wasPaused = reflexPaused;
+			reflexPaused = true;
+			const deadline = Date.now() + 120_000;
+			const tryDispatch = () => {
+				if (!reflexCtx.busy) {
+					info("ipc", `run-skill: dispatching ${skillId}`);
+					dispatchAction(() => runSkill(skillId, reflexCtx, args), `ipc:${skillId}`, {
+						onComplete: (res) => {
+							reflexPaused = wasPaused;
+							send(EVENT_TYPES.LOG, {
+								ts: new Date().toISOString(),
+								level: "info",
+								source: "run-skill",
+								text: `${skillId} → ${res.code ?? (res.ok ? "ok" : "fail")}`,
+								details: res,
+							});
+						},
+					});
+					return;
+				}
+				if (Date.now() > deadline) {
+					reflexPaused = wasPaused;
+					send(EVENT_TYPES.ERROR, { source: "run-skill", text: `still busy after 2 min with ${reflexCtx.currentActionLabel}` });
+					return;
+				}
+				setTimeout(tryDispatch, 500);
+			};
+			tryDispatch();
+			break;
+		}
 		default:
 			warn("ipc", `unknown command type: ${msg.type}`);
 	}