fix(parsers/php,ruby): keep both same-name defs from conditional/guarded branches

[gadievron]

Companion to #121 (the C/C++ same-(file,name) collision fix). A blind independent re-derivation + an adversarial judge — both running the real php/ruby/node interpreters — established that of the non-C parsers, only PHP and Ruby have a harmful same-name collision; JS and Python do not (JS keeps the last-wins copy / skips conditional defs; Python already keeps both via a #L<line> suffix). This PR fixes PHP and Ruby; it deliberately does not touch JS/Python.

The bug (PHP + Ruby)

A PHP function/Ruby def in a mutually-exclusive conditional branch is runtime-reachable depending on the environment, and the earlier-in-source branch is often the live one:

if (!function_exists('h')) { function h(){ return real(); } }      // runs when h is undefined
if (!function_exists('h')) { function h(){ return fallback(); } }  // skipped

if COND then def k; if_branch; end else def k; else_branch; end end

Both extractors keyed on qualified_name with a plain keep-last store, so the later (often dead) branch silently overwrote the earlier (often live) one — a false negative for a SAST tool. Confirmed: php prints real() / ruby runs if_branch, but the extractor kept the other branch.

The fix — keep BOTH (not prefer-first/larger)

Which branch is live is environment-dependent, so neither is statically dead. The fix keeps both via a deterministic #L<line> suffix (earlier-in-source keeps the clean id) — the exact _store_function strategy the Python extractor already uses, which is precisely why Python was found immune. Ported into the PHP (:558, :600) and Ruby (:549, :613) store sites.

• Collision-only: a unique name keeps its byte-identical path:name id (pinned by a test_unique_name_id_unchanged per language).
• PHP: plain redefinition is a fatal error, so the only same-name duplicates are conditional/guarded — keep-both is purely beneficial there.
• Ruby: unconditional reopening is last-wins at runtime; keeping both there is the same benign tradeoff Python accepts (Stage 2 attacker-simulation filters dead overrides).

Tests

New: tests/parsers/php/test_php_conditional_collision.py, tests/parsers/ruby/test_ruby_conditional_collision.py.

$ pytest tests/parsers/php/ tests/parsers/ruby/ -q
83 passed

Full repo suite: 606 passed, 22 skipped.