fix(php-extractor): capture file-scope calls + map include/require as imports (#367)

[tirth8205]

Summary

Fixes two extractor bugs that caused ~0% call-graph + import coverage on procedural (page-style) PHP — the dominant style outside Composer/PSR-4 projects (#367).

Bug A — top-level calls dropped. extractCallGraph() only recorded a call when functionStack.length > 0, so any function_call_expression / member_call_expression / scoped_call_expression at file scope produced no entry. On procedural PHP, that meant the call graph was empty.

Fix: when functionStack is empty, attribute the call to a synthetic <file> caller (a stable, language-neutral identifier) so file→callee edges are still emitted.

Bug B — include / require not mapped. extractStructure() only looked at namespace_use_declaration for imports. include, include_once, require, and require_once — the file→file dependency mechanism for non-namespaced / legacy PHP — were ignored.

Fix: recognise expression_statement children whose inner node is include_expression / include_once_expression / require_expression / require_once_expression. Walk the path argument:

• String literal ('config.php', "lib/util.php") → captured as-is.
• Magic-constant concatenation (__DIR__ . '/helpers.php') → reconstructed by recursing into binary_expression and preserving __DIR__ / __FILE__ verbatim so the consumer can resolve relative to the current file.
• Non-resolvable expressions (variables, function calls) → emitted with the raw argument text so the dependency edge isn't silently lost.

Test plan

All 35 tests in php-extractor.test.ts pass (29 pre-existing + 6 new).

New tests cover:

• attributes top-level calls to the synthetic <file> caller (#367) — main(), $obj->run(), Helper::go() at file scope all captured under <file>.
• mixes file-scope and in-function calls in a single file (#367) — <file>-scope bootstrap() + handleRequest() and in-function process_input() both appear with correct callers.
• captures include/require with a plain string literal as imports (#367) — all four variants (include, include_once, require, require_once) produce import entries.
• resolves __DIR__ . '/path' concatenation in require_once (#367) — produces source "__DIR__/helpers.php".
• captures include/require alongside use statements (#367) — coexists with namespace_use_declaration extraction.
• records non-resolvable include path as raw text (#367) — include $path; still emits an entry.

Existing behaviour (in-function calls, instance/static method calls, use imports, grouped/aliased use, block-scoped namespaces, return types, exports) is preserved — the original test that asserted top-level calls were silently dropped was updated to reflect the new (correct) behaviour.

Verification commands run:

• pnpm test --root understand-anything-plugin/packages/core php-extractor → 35/35 pass, 0 type errors (--typecheck).
• pnpm lint → clean.

Closes #367.