fix: slim CLI package and enforce clean linting

[chtnnh]

Summary

This change makes the published @chtnnh/know-code package materially leaner while adding a maintained lint gate for the repository.

• Excludes compiled test modules, test declaration files, source maps, and test helpers from the CLI npm tarball.
• Adds a package-contents regression test so runtime artifacts (bin/, hooks, and dist/index.js) remain shipped while test-only output stays out.
• Introduces Biome configuration and npm scripts, then runs lint in CI before build and test.
• Resolves the CLI lint findings with explicit validated narrowing, and removes stale imports and unused bindings, including the obsolete Umami proxy import.

Why

npm pack --dry-run showed that the published CLI artifact included compiled test files and test helpers that are never required by global installations. Keeping the package focused on runtime files reduces install/download overhead without changing the public CLI surface.

Validation

• npm run lint -- --max-diagnostics=100
• git diff --check

Closes #5

[cursor]

PR Summary

Low Risk
Tooling, package-contents, and lint-driven refactors; no change to auth, gating policy, or public CLI behavior.

Overview
Keeps the published @chtnnh/know-code tarball to runtime files only, and adds a Biome lint gate so those hygiene rules stay enforced.

packages/cli now excludes compiled tests, test helpers, and source maps from files. A new pack dry-run test asserts bin/, hooks, and dist/index.js still ship.

Adds biome.json, root lint/lint:fix/format:check scripts, and runs npm run lint in CI before build. CLI lint findings are cleaned up with explicit null checks (especially around grade answersDigest) and unused imports/bindings.

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[cursor]

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