chore(release): v1.6.1.0 — Opus 4.7 migration, reviewed

Bump VERSION + package.json from 1.6.0.0 to 1.6.1.0. New CHANGELOG
entry describing the ship-quality remediation of PR #1117:

- Overlay split (model-agnostic claude.md + opus-4-7.md with INHERIT)
- Routing-injection aligned with SKILL.md.tmpl ("when in doubt" policy,
  current skill names, full skill inventory)
- utility.ts trailer fallback updated
- Voice example closes through review gate instead of ship-bypass
- Literal-interpretation nudge bounded to branch scope
- Batch-questions nudge has explicit pacing exception
- First Opus 4.7 eval: routing verified 3/3, fanout A/B unverified
  under `claude -p` (tracked as P0 TODO for next rev)
- Pre-existing test failures fixed: fs.statSync binary guard, 180s
  setup timeout, golden-file updates

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.6.0.0",
+  "version": "1.6.1.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",