fix(discovery): setuptools build output (build/lib) analyzed as project code

[rahlk]

Plan (optional)

None — small scoping fix.

Problem

File discovery (codeanalyzer/core.py ~line 870) walks project_dir.rglob("*.py") and skips only site-packages, .venv, and .codeanalyzer path parts. A project built with setuptools carries build/lib/** — byte copies of its package sources — so every module is analyzed twice (once under its real path, once under build/lib/...), inflating the symbol table and downstream graphs. Same bug class just fixed in codeanalyzer-java, where Gradle's build/resources copies of test fixtures leaked into analysis (codellm-devkit/codeanalyzer-java#199); found during that fix's propagation sweep. dist/ (sdist/wheel staging) and *.egg-info are worth the same look.

Scope boundary

Discovery filter only. No schema change, no change to what a module contains — only which files become modules.

Goals

• build/lib (and dist, *.egg-info if confirmed) excluded from discovery
• Failing test first: fixture with a build/lib copy of a real module yields one module, not two

Caveats and known risks

• A project with hand-written sources under a top-level build/ package would lose them — accepted, collides with setuptools' own output convention.

Definition of done

• Test fails before / passes after; module count over the fixture equals the hand-counted set
• Full test suite green