chore: post-merge cleanup of #941 review nits

[mldangelo]

Summary

Follow-up to #941 with the remaining low-priority items from the review that didn't make it into the merged commit.

• Extract isDirectory helper into src/utils/fs.ts; remove duplicated copies in src/main.ts and src/utils/config.ts.
• Drop the unnecessary String(...) cast around compareBase in src/main.ts (GitHub Action inputs are already strings).
• Normalize dist artifact paths inside listFiles() in the rebuild workflow, eliminating two downstream .replace() calls on the result.
• Refresh stale AGENTS.md note — action already runs on node20.

No behavior changes; pure cleanup.

Test plan

• `npm run lint` — clean
• `npm test` — 149/149 pass
• `npm run build` — clean
• `npm run package` — dist regenerated

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Refactors the isDirectory helper into a shared utility module to eliminate duplication between src/main.ts and src/utils/config.ts. Also includes minor cleanup in src/main.ts, an AGENTS.md note update, and path normalization simplification in a workflow file.

Changes:

• Extracted isDirectory into new src/utils/fs.ts and imported it from both main.ts and config.ts.
• Simplified compareBase assignment in main.ts (removed redundant String() wrapper).
• Normalized dist file paths at listing time in the dependabot workflow, removing duplicated replace calls.

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/utils/fs.ts	New shared utility module exporting isDirectory.
src/utils/config.ts	Removed local isDirectory and imported from new module.
src/main.ts	Removed local isDirectory, imported shared one; simplified compareBase.
dist/index.js	Regenerated bundle reflecting the source changes.
AGENTS.md	Updated note to reflect Node 20 runtime.
.github/workflows/dependabot-post-update.yml	Normalize dist paths once at listing instead of at each use.

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