ci: add GitHub Agentic Workflows scaffolding + daily hygiene assessment

Adds gh-aw (GitHub Agentic Workflows) framework files plus an AI-driven
daily hygiene-assessment workflow that scans main for:
  1. Workaround patterns (CLAUDE.md forbids without approval)
  2. Ungrounded retail-port code (no decomp citation)
  3. Roadmap / phase / CLAUDE.md "currently working toward" drift
  4. Test / build hygiene (warnings, test count regression)
  5. Architecture drift (cross-layer references, WB imports outside Wb/)

Output: one rolling GitHub issue per day, labelled ai+hygiene; the
framework auto-closes the prior day's report. Engine: copilot
(gpt-5.3-codex) — uses your Copilot subscription, no separate API key
needed.

Scaffolding from gh aw init:
  - .gitattributes          (marks .lock.yml as generated)
  - .github/agents/         (dispatcher agent)
  - .github/mcp.json        (MCP server config)
  - .github/workflows/aw.json (ghes:false — we target GitHub.com)
  - .github/workflows/copilot-setup-steps.yml
  - .vscode/settings.json   (editor settings)

Workflow:
  - .github/workflows/hygiene-assessment.md     (human-authored source)
  - .github/workflows/hygiene-assessment.lock.yml (compiled artifact)

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

.gitattributes

@@ -0,0 +1 @@
+.github/workflows/*.lock.yml linguist-generated=true merge=ours