fix: reduce dead code false positives

[gzenz]

Summary

• Extract decorators/annotations from AST into node.extra["decorators"] for Python, Java/Kotlin/C#, and TypeScript -- enables framework entry point detection that was previously wired but never populated
• Expand _FRAMEWORK_DECORATOR_PATTERNS from 8 to 22 patterns (pytest fixtures, Django signals, SQLAlchemy events, Celery tasks, Spring annotations, Flask/Starlette middleware, NestJS/Angular decorators)
• Exclude dunder methods (__init__, __str__, etc.) from dead code results -- runtime-invoked, never have explicit callers
• Skip classes referenced in function type annotations (Pydantic schemas, dataclasses used as param/return types)

Test plan

• 2 parser tests: decorator extraction for Python functions and classes
• 4 flows tests: new decorator patterns (pytest, Django, Spring, Celery)
• 4 refactor tests: dunder exclusion, decorated entry points, type-ref via params, type-ref via return type
• Full suite: 575 passed, 0 failures

[tirth8205]

Great improvement to dead code detection accuracy — expanding framework patterns from 8 to 22, excluding dunder methods, and using AST decorators are all valuable. 314 lines of new tests.

Please rebase on latest main. Once rebased and CI passes, we'll review for merge.

[tirth8205]

Review: PR #104 — fix: reduce dead code false positives (DRAFT)

This PR is superseded by PR #158, which incorporates this fix (decorator extraction, expanded framework patterns, dunder exclusion, type annotation reference tracking) and many more improvements from the same author.

Recommendation: Close this PR in favor of #158. gzenz confirmed in #103's comments that they consolidated all improvements into one large PR (#158). The owner's review comment also asked for a rebase, which was never done.

Note: This PR is still in DRAFT status.

[gzenz]

Superseded by #158.