fix: add PHP grammar support to smart-file-read parser (fixes #1617)

PHP was listed as a supported language in CHANGELOG and .php files were
scanned by search.ts, but parser.ts was missing:
- .php extension in LANG_MAP (causing detectLanguage to return 'unknown')
- 'php' entry in GRAMMAR_PACKAGES (no grammar path to resolve)
- PHP query patterns for symbol extraction
- PHP case in getQueryKey()

This meant smart_search/smart_outline/smart_unfold scanned PHP files
but extracted 0 symbols because the grammar could not be resolved.

Changes:
- Add '.php' -> 'php' to LANG_MAP
- Add 'php' -> 'tree-sitter-php/php' to GRAMMAR_PACKAGES
- Add PHP tree-sitter query patterns (functions, methods, classes, interfaces, traits, use statements)
- Add 'php' case to getQueryKey()
- Add tree-sitter-php ^0.24.2 to devDependencies

package.json

@@ -138,6 +138,7 @@
     "tree-sitter-go": "^0.25.0",
     "tree-sitter-java": "^0.23.5",
     "tree-sitter-javascript": "^0.25.0",
+    "tree-sitter-php": "^0.24.2",
     "tree-sitter-python": "^0.25.0",
     "tree-sitter-ruby": "^0.23.1",
     "tree-sitter-rust": "^0.24.0",