feat(v1.5.2.0): Opus 4.7 migration — model overlay, voice, routing

Adapts GStack skill text for Claude Opus 4.7's behavioral changes per
Anthropic's migration guide and community findings.

Key changes:

model-overlays/claude.md:
  - Fan out explicitly (4.7 spawns fewer subagents by default)
  - Effort-match the step (avoid overthinking simple tasks at max)
  - Batch questions in one AskUserQuestion turn
  - Literal interpretation awareness (deliver full scope)

hosts/claude.ts:
  - coAuthorTrailer updated to Claude Opus 4.7

SKILL.md.tmpl:
  - Expanded routing triggers with colloquial variants ("wtf",
    "this doesn't work", "send it", "where was I") — 4.7 won't
    generalize from sparse trigger patterns like 4.6 did
  - Added missing routes: /context-save, /context-restore, /cso, /make-pdf
  - Changed routing fallback from strict "do NOT answer directly" to
    "when in doubt, invoke the skill" — false positives are cheaper
    than false negatives on 4.7's literal interpreter

generate-voice-directive.ts:
  - Added concrete good/bad voice example — 4.7 needs shown examples,
    not just described tone. "auth.ts:47 returns undefined..." vs
    "I've identified a potential issue..."

Regenerated all 38 SKILL.md files. All tests pass.

hosts/claude.ts

@@ -38,7 +38,7 @@ const claude: HostConfig = {
     linkingStrategy: 'real-dir-symlink',
   },
 
-  coAuthorTrailer: 'Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>',
+  coAuthorTrailer: 'Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>',
   learningsMode: 'full',
 };