build(web): replace Playwright MCP with project-scoped Playwright CLI

- feat: add `.agents/skills/playwright-cli/` with complete Skill
  markdown, agent interface, and 9 reference files covering session
  management, spec-driven testing, video recording, tracing, storage,
  request mocking, element attributes, test debugging, and running
  custom code
- feat: add `.playwright/cli.config.json` to configure the Playwright
  CLI
- feat: add `web/package.json` `playwright:cli` script that resolves
  `playwright cli` from the repo root
- build: remove `@playwright/mcp` dependency from `web/package.json`
- build: set `XDG_CACHE_HOME` in `mise.toml`
- build: delete `.codex/config.toml` (MCP server config)
- docs: update `README.md`, `docs/web/roadmap.md`,
  `docs/web/decisions.md`, and `web/README.md` to reflect the new
  Playwright CLI approach

web/package.json

@@ -13,7 +13,7 @@
     "lint": "oxlint",
     "playwright:install": "playwright install chromium",
     "playwright:install:deps": "playwright install-deps chromium",
-    "playwright:install:mcp": "node node_modules/playwright/cli.js install chromium",
+    "playwright:cli": "cd .. && playwright cli",
     "test": "vitest run",
     "test:e2e": "playwright test",
     "typecheck": "tsc -b",
@@ -29,7 +29,6 @@
     "react-router": "^8.2.0"
   },
   "devDependencies": {
-    "@playwright/mcp": "0.0.78",
     "@playwright/test": "1.61.1",
     "@tailwindcss/vite": "^4.3.2",
     "@types/node": "^24.13.2",