feat: Add complete PHP language support with trait handling and property extraction

Addresses PHP traits extracted as classes, missing class properties, skipped constants, and invisible trait usage. Adds classifyClassNode to distinguish traits from classes, fixes property extraction for PHP's property_element AST structure (added 4,366 field nodes), and adds visitNode hook for class constants and trait use declarations (increased trait edges from 636 to 1,514). Also improves Liquid schema name handling and file path reference resolution. Verified against Laravel codebase.

docs/SEARCH_QUALITY_LOOP.md

@@ -460,6 +460,10 @@ test().catch(console.error);
 | Svelte `$state`/`$derived` rune calls creating noise | Runes are compiler builtins, not real function calls | `src/extraction/svelte-extractor.ts` filters `SVELTE_RUNES` set from unresolved references |
 | Object literal getters/setters extracted as standalone functions | `method_definition` inside `object` literals treated same as class methods | `src/extraction/tree-sitter.ts: extractMethod` skips `method_definition` nodes whose parent is `object`/`object_expression` |
 | JavaScript `class extends` produces zero inheritance edges | JS tree-sitter uses `class_heritage → identifier` (bare), not `class_heritage → extends_clause → identifier` like TypeScript | `src/extraction/tree-sitter.ts: extractInheritance` — handle bare `identifier`/`type_identifier` children when parent is `class_heritage` |
+| PHP traits extracted as classes | `trait_declaration` in `classTypes` but `extractClass` hardcodes `class` kind | `src/extraction/languages/php.ts: classifyClassNode` returns `'trait'` for `trait_declaration`; `src/extraction/tree-sitter-types.ts` adds `'trait'` to return type |
+| PHP class properties missing (0 field nodes) | `extractField` looks for `variable_declarator` children; PHP uses `property_element > variable_name > name` | `src/extraction/tree-sitter.ts: extractField` — handle `property_element` children with `variable_name > name` path |
+| PHP class constants skipped inside classes | `variableTypes` check has `!isInsideClassLikeNode()` guard, so `const_declaration` inside classes falls through | `src/extraction/languages/php.ts: visitNode` hook catches `const_declaration`, extracts `const_element > name` as `constant` kind |
+| PHP `use TraitName` inside classes invisible | `use_declaration` nodes in class body not processed for edges | `src/extraction/languages/php.ts: visitNode` hook extracts trait names from `use_declaration` and creates `implements` unresolved references |
 
 ## After Fixing Issues
 
@@ -547,6 +551,7 @@ if (receiverType) {
 - [x] **Dart** — NOT needed for `getReceiverType`. Methods nested in class body. Added bare call extraction for selector-based method calls (e.g. `object.method()`). Verified against Flutter
 - [x] **Kotlin** — `getReceiverType` extracts receiver from extension functions `fun Type.method()`. Added `classifyClassNode` to distinguish interfaces/enums from classes (all use `class_declaration` AST node). Added `resolveBody` hook since Kotlin's tree-sitter grammar doesn't use field names. Added `navigation_expression` handling for method call extraction. Added `object_declaration` via `extraClassNodeTypes`. Added `delegation_specifier` handling in `extractInheritance` for Kotlin's `: Parent, Interface` syntax. Also fixed `extractInterface` to visit body children (interface methods were not being extracted). Added `visitNode` hook to handle `fun interface` (SAM) declarations — tree-sitter-kotlin doesn't support this Kotlin 1.4+ syntax, producing ERROR or function_declaration misparse; the hook detects both patterns and extracts the interface. Verified against Koin, LeakCanary
 - [x] **Svelte** — Custom `SvelteExtractor` delegates `<script>` blocks to TS/JS parser; creates `component` nodes for each `.svelte` file. Added template expression call extraction: scans `{expression}` blocks in markup for function calls (e.g. `class={cn(...)}`), creating call edges from component to callees — increased Svelte call edges from 29 to 387. Filtered Svelte 5 rune calls (`$state`, `$props`, `$derived`, `$effect`, `$bindable`). Also fixed: destructured `$props()` patterns (e.g. `let { x, y } = $props()`) no longer extracted as ugly multi-line variable names (skip `object_pattern`/`array_pattern` in `extractVariable`). Object literal getter/setter methods no longer extracted as standalone functions. Verified against shadcn-svelte
+- [x] **PHP** — NOT needed for `getReceiverType`. Methods nested in class body. Added `classifyClassNode` to distinguish traits from classes (`trait_declaration` → `trait` kind). Added `'trait'` to `classifyClassNode` return type in `tree-sitter-types.ts` and handling in visitor. Fixed PHP property extraction: `extractField` now handles `property_element > variable_name > name` AST structure (added 4,366 field nodes). Added `visitNode` hook for class constants (`const_declaration` inside classes was skipped by `variableTypes` guard) and trait `use` declarations (`use HasFactory, SoftDeletes;` creates `implements` edges — increased from 636 to 1,514). Verified against Laravel
 
 ### Needs Verification