chore: drop Laravel Boost; make AGENTS.md the canonical agent doc

- Remove laravel/boost (+ its deps laravel/mcp, laravel/roster) and Boost's
  .cursor/ skills + MCP registration. No version sweep (composer remove).
- AGENTS.md is now the hand-maintained source of truth (was Boost-generated):
  folds in the CLAUDE.md content + a Conventions section codifying the migration
  FK rule (unsignedInteger for INT-PK refs, not foreignId — MySQL error 3780)
  and the MySQL/PostgreSQL/SQLite cross-DB requirement.
- CLAUDE.md / GEMINI.md / .github/copilot-instructions.md are now gitignored
  symlinks to AGENTS.md, created by bin/ai-docs.php (composer run ai-docs, also
  wired into post-autoload-dump).

composer.json

@@ -37,7 +37,6 @@
         "barryvdh/laravel-ide-helper": "^3.5",
         "fakerphp/faker": "^1.23",
         "jasonmccreary/laravel-test-assertions": "^2.9",
-        "laravel/boost": "^2.3",
         "laravel/pint": "^1.13",
         "laravel/sail": "^1.41",
         "mockery/mockery": "^1.6",
@@ -66,9 +65,11 @@
     "scripts": {
         "lint": "pint --test",
         "lint:fix": "pint",
+        "ai-docs": "@php bin/ai-docs.php",
         "post-autoload-dump": [
             "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
-            "@php artisan package:discover --ansi"
+            "@php artisan package:discover --ansi",
+            "@php bin/ai-docs.php"
         ],
         "post-update-cmd": [
             "@php artisan vendor:publish --tag=laravel-assets --ansi --force"