feat: add bootcamp impact for change-impact ("blast radius") analysis

[Arthur742Ramos]

Summary

Adds bootcamp impact <repo-url> [file] — a standalone, deterministic change-impact / blast-radius report that exposes the existing buildImportGraph / analyzeChangeImpact engine (the same one that produces IMPACT.md) as a first-class command. No LLM involved.

🎯 src/util.ts
  imported by 1 · affects 1 file · 1 test · 0 docs

Imports (0)
  —
Imported by (1)
  • src/index.ts
Affected tests (1)
  • test/util.test.ts
…

Details

• With a <file> argument — full blast radius for that file: what it imports, what imports it, and the transitively affected files, tests, and docs.
• Without a file — summarizes the repository's key entry-point files (bounded by --top, default 10), each with a one-line impact count.
• --json emits the full ChangeImpact objects for scripting.
• A repo-relative path is normalized to the scan's forward-slash keys; a path that wasn't scanned exits non-zero with a helpful message (and still cleans up the temporary clone).

This completes the standalone deterministic command set: scan/health/metrics/security/deps/radar/impact.

Depends on #67 (import-resolution fix) — without it, dependents wouldn't resolve for TS/ESM projects and the blast radius would read empty.

Testing

• Unit: key-file summary, single-file detail, --top bound, --json, ./-path normalization, not-found exit (with cleanup), no-key-files message, --keep-temp, scan failure, resolve failure — 10 tests.
• E2E: bootcamp impact against a real local fixture with a genuine import edge — summary, single-file detail + JSON (importedBy contains the dependent), and not-found exit — 3 tests.
• Full suite green locally: typecheck, lint, build, 1177/1177 unit tests.

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