Add composite god-file / kitchen-sink module detector

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Summary

Add a composite "god file" / kitchen-sink module detector that flags modules doing too much by combining multiple existing signals — large size, many exports, and high responsibility spread — into one finding.

Motivation

DebtLens already detects individual symptoms (large-function, api-surface-sprawl, barrel-file). But a module can pass each individual threshold while still being an unmaintainable catch-all. A composite rule that fires when several signals co-occur catches the "everything lives here" file that single-axis rules miss.

Proposed behavior

• god-file: fires when a module crosses a combination of thresholds, e.g. total lines + export count + number of top-level functions/classes + distinct concern indicators (mixed I/O, UI, and domain logic).
• Confidence scales with how many independent axes are exceeded.
• Suggestion: split by responsibility, extract cohesive submodules, define a clear public entrypoint.

Config: godFile.maxLines, godFile.maxExports, godFile.maxTopLevelDecls, and the minimum number of axes required to fire.

Implementation surface

• New src/detectors/godFile.ts that reuses metrics computed by apiSurfaceSprawl.ts and the size logic in largeFunction.ts / src/utils/lines.ts.
• Register in src/detectors/index.ts; include in core pack.
• Docs in docs/rules.md; fixtures: a true god file vs a large-but-cohesive module (must not fire on the latter).

Acceptance criteria

• Fires only when multiple axes are exceeded (configurable minimum).
• Does not fire on large-but-cohesive single-purpose modules.
• Confidence reflects number of axes exceeded.
• Documented + npm run test:all passes.

Difficulty: medium.