feat: add github-native coordination (epic-* commands + scripts + tests)

Adds a GitHub-native coordination layer on top of ECC:

Commands (7 new slash commands):
- epic-claim, epic-sync, epic-validate, epic-publish
- epic-review, epic-unblock, epic-decompose

Scripts:
- scripts/github-coordination.js  — CLI entry point
- scripts/lib/github-coordination.js  — core library (state machine, gh API wrappers)
- scripts/status.js  — coordination status reporter

Config:
- config/github-native-coordination.json  — labels, review policy, validation gates

Tests:
- tests/lib/github-coordination.test.js  — 15 unit tests for pure functions
- tests/scripts/github-coordination.test.js  — integration/CLI test suite

Registry:
- docs/COMMAND-REGISTRY.json  — adds 7 epic-* entries, totalCommands 84 → 91

No encoding changes, no prp-* modifications, no Windows shims.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/COMMAND-REGISTRY.json

@@ -1,6 +1,6 @@
 {
   "schemaVersion": 1,
-  "totalCommands": 84,
+  "totalCommands": 91,
   "commands": [
     {
       "command": "aside",
@@ -111,6 +111,72 @@
       ],
       "path": "commands/ecc-guide.md"
     },
+    {
+      "command": "epic-claim",
+      "description": "Claim an epic issue, stamp coordination state, and sync local ownership.",
+      "type": "review",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [
+        "orch-add-feature",
+        "orch-change-feature"
+      ],
+      "path": "commands/epic-claim.md"
+    },
+    {
+      "command": "epic-decompose",
+      "description": "Break an epic into task children without creating task branches.",
+      "type": "review",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-decompose.md"
+    },
+    {
+      "command": "epic-publish",
+      "description": "Publish a validated epic update back to the issue and local cache.",
+      "type": "general",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-publish.md"
+    },
+    {
+      "command": "epic-review",
+      "description": "Mark epic review requested, approved, or changes requested.",
+      "type": "review",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-review.md"
+    },
+    {
+      "command": "epic-sync",
+      "description": "Sync epic issue bodies, labels, and local coordination snapshots from GitHub.",
+      "type": "general",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-sync.md"
+    },
+    {
+      "command": "epic-unblock",
+      "description": "Sweep blocked epic issues and reopen anything whose dependencies are closed.",
+      "type": "general",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-unblock.md"
+    },
+    {
+      "command": "epic-validate",
+      "description": "Validate epic readiness, dependencies, and coordination policy.",
+      "type": "review",
+      "primaryAgents": [],
+      "allAgents": [],
+      "skills": [],
+      "path": "commands/epic-validate.md"
+    },
     {
       "command": "evolve",
       "description": "Analyze instincts and suggest or generate evolved structures",