chore: extract AGENTS.md recipes into agent skills

Closes #2163

`AGENTS.md` was one 1,223-line contract loaded in full on every turn, whether
the task was a one-line CSS fix or a release cut. This splits it: rules stay
resident, procedures move to `.claude/skills/`.

- Ten skills under `.claude/skills/`, seven `disable-model-invocation: true`
  (invoked by name only, so they cost no listing context and have no trigger
  question) and three model-invoked with committed eval cases.
- `AGENTS.md` 1,223 → 380 lines: rules, a skills index, and a project tree
  reduced to one line per entry. The removed recipes are not duplicated.
- `README.md` 811 → 105 lines, split into `docs/{architecture,quality-gate,
  test-servers,publishing,docker}.md`, and dropped from `CLAUDE.md`'s auto-load.
- `.github/copilot-instructions.md` and its mirroring rule removed — Copilot
  reads `AGENTS.md`.
- `npm run verify:skills` (in `validate`, so in `local:gate` and CI) parses each
  SKILL.md the way Claude Code does, requires an explicit invocation mode and
  eval cases for model-invoked skills, and budgets the listing.
- `npm run skills:eval` runs the committed trigger cases headless.

Signed-off-by: cliffhall <cliff@futurescale.com>

package.json

@@ -43,8 +43,9 @@
     "verify:build-gate": "node scripts/verify-build-gate.mjs",
     "verify:bundle-externals": "node scripts/verify-bundle-externals.mjs",
     "verify:typecheck-coverage": "node scripts/verify-typecheck-coverage.mjs",
+    "verify:skills": "node scripts/verify-skills.mjs",
     "test:scripts": "node --test \"scripts/**/*.test.mjs\"",
-    "validate": "npm run verify:format-coverage && npm run verify:typecheck-coverage && npm run verify:dep-lockstep && npm run test:scripts && npm run validate:core && npm run validate:web && npm run validate:cli && npm run validate:tui && npm run validate:launcher",
+    "validate": "npm run verify:format-coverage && npm run verify:skills && npm run verify:typecheck-coverage && npm run verify:dep-lockstep && npm run test:scripts && npm run validate:core && npm run validate:web && npm run validate:cli && npm run validate:tui && npm run validate:launcher",
     "verify:format-coverage": "node scripts/verify-format-coverage.mjs",
     "verify:dep-lockstep": "node scripts/verify-dep-lockstep.mjs",
     "validate:core": "npm run format:check:core && npm run format:check:scripts && npm run format:check:shared && npm run lint:core && npm run lint:shared",
@@ -81,7 +82,8 @@
     "smoke:launcher": "node scripts/smoke-launcher.mjs",
     "pack:verify": "node scripts/install-smoke-browser.mjs chromium && node scripts/pack-and-verify.mjs",
     "prepack": "npm run build",
-    "postinstall": "node scripts/install-clients.mjs"
+    "postinstall": "node scripts/install-clients.mjs",
+    "skills:eval": "node scripts/skill-eval.mjs"
   },
   "dependencies": {
     "@hono/node-server": "^2.0.12",