feat: add --exclude CLI flag to /understand for user-defined ignore p…

[yiziff]

…atterns

• createIgnoreFilter() now accepts optional extraPatterns array (Layer 4, highest priority)
• scan-project.mjs parses --exclude from CLI args and passes patterns through
• project-scanner.md documents --exclude flag usage
• SKILL.md wires --exclude into Phase 0/1 and updates argument-hint
• 5 new test cases covering CLI priority, ! negation, and .understandignore interaction

Related: #76

Summary

Linked issue(s)

How I tested this

• pnpm lint
• pnpm --filter @understand-anything/core test
• pnpm test
• Manual smoke test (describe above)

Versioning

• Version bumped in all five manifests, OR
• N/A — internal/docs-only change

[yiziff]

"Hi @Lum1104
Just checking in on this PR. I notice that other ongoing issues (like #466) have already mentioned this --exclude feature as part of the project's scalability roadmap.

Is there anything else I need to optimize, or any edge cases/tests I should add to get this merged? Thanks!"

[tirth8205]

Reviewed the full diff, checked out the branch, and ran the tests.

Verdict: correct and well-scoped. The feature does what it claims.

What I verified:

• createIgnoreFilter(projectRoot, extraPatterns = []) adds CLI patterns as Layer 4 after defaults and both .understandignore files, so they get highest priority and ! negation works in both directions. Backward compatible — existing single-arg callers are unaffected.
• scan-project.mjs arg parsing is order-independent and defensive. I confirmed --exclude works before or after the positionals, and a trailing value-less --exclude is harmlessly ignored (the i + 1 < length guard prevents it from swallowing a positional).
• Glob semantics are delegated to the ignore lib, so gitignore syntax is consistent with the rest of the system. End-to-end on a real repo, --exclude "tests/*,docs/*" dropped both dirs and reported filteredByIgnore=2; --exclude "!dist/" re-included a default-excluded dir.
• Tests: all 22 ignore-filter tests pass, full core suite 675/675, lint clean. The 5 new cases are meaningful (priority over .understandignore, ! re-include, combination, empty-array no-op).

One thing worth a doc note (not blocking):

--exclude only takes effect on the full-scan path. It flows through Phase 1 (project-scanner → scan-project.mjs) but is not persisted to config.json (unlike --language), and the incremental-update path (git diff --name-only → compute-batches.mjs) never consults it. Practical consequence: on a first full run the excludes hold (excluded files never enter the graph, so later incremental updates ignore them anyway), but you cannot newly add --exclude on an incremental run to drop files already in the graph — that requires --full. A one-line note in the --exclude help text or SKILL.md ("newly-added excludes require --full to take effect") would set the right expectation.

Otherwise this is good to merge.

[yiziff]

Thanks for the thorough review and testing, @tirth8205 ! I completely agree with the incremental scan behavior. I've just pushed a commit to update SKILL.md with that exact warning about needing --full to apply new exclusions. Let me know if it looks good to go!