build: 移植 PHPCS + PHPStan L6 品質 gate（PR-I 前半）

- phpcs.xml（自 A 移植）：ruleset 改名、*/tools/* 例外換成 */back-compat/*、
  中文註解全域排除 Squiz.Commenting.InlineComment.InvalidEndChar、
  interface 別名檔排除 OneObjectStructurePerFile
- 檔頭正規化：16 個檔案的 declare(strict_types=1) 與前導 // 註解移到
  file docblock 之後，並移除 <?php 後多餘空行（phpcbf 另自動修 190 處）
- phpstan.neon + .phpstan/stubs.php（TMDO_ 與 WPDO_ 兩套常數）+
  重新產生的 phpstan-baseline.neon（710 errors，A 的 3877 行 baseline
  因前綴與路徑不同無法沿用）

現況：PHPCS 0 errors / 0 warnings、PHPStan L6 No errors、
unit 451 / integration 398 GREEN

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TbG1keQQ7XBa7qMQY16KCY

phpstan.neon

@@ -0,0 +1,29 @@
+includes:
+    - vendor/szepeviktor/phpstan-wordpress/extension.neon
+    # Baseline: existing type-completeness debt (mostly missing iterable value
+    # types + WP template-scope variables). New code is checked clean at L6.
+    # Burn down incrementally; regenerate with `composer stan:baseline`.
+    - phpstan-baseline.neon
+parameters:
+    level: 6
+    paths:
+        - includes
+        - admin
+        - cli
+        - modules
+        - 2meet-data-optimizer.php
+        - uninstall.php
+    bootstrapFiles:
+        # Plugin constants (define()'d at runtime; PHPStan can't see them).
+        - .phpstan/stubs.php
+    scanFiles:
+        # WP-CLI classes/functions (runtime-injected by wp-cli; use official stubs).
+        - vendor/php-stubs/wp-cli-stubs/wp-cli-stubs.php
+    excludePaths:
+        - vendor
+        - tests
+        - .phpstan
+        # interface wrappers: PHPStan sees WPDO_X extends TMDO_X as circular
+        - includes/back-compat
+    reportUnmatchedIgnoredErrors: false
+    treatPhpDocTypesAsCertain: false