feat(workspace): add file-tree add-to-chat action

[DerrickBarra]

Summary

Implements the next small stacked attachment slice after the canonical contract and composer simplification work by adding a workspace file-tree Add to chat action for existing workspace files.

Stacking / dependency

This PR is intentionally stacked on top of:

• feat(attachments): add canonical upload reference contract #229 — canonical attachment contract
• feat(chat): make paperclip the primary upload flow #231 — composer single-primary-paperclip simplification

If those earlier slices change materially, this PR will be revised accordingly.

What changed

• adds a file-tree context-menu Add to chat action for existing workspace files
• routes that action through the existing chat attachment handoff path
• keeps the resulting attachment in the canonical workspace-reference flow
• adds focused tests for file-only visibility/behavior

Deliberately not included

To keep this slice small and reviewable, it does not include:

• directory-as-context behavior
• optimization / derivative generation
• unrelated composer UX changes beyond the existing stacked base
• unrelated local/debug workflow surfaces

Verification

• src/features/file-browser/FileTreePanel.test.tsx
• src/features/chat/InputBar.test.tsx
• tsc -p tsconfig.json --noEmit

Related to #232
Depends on #229
Depends on #231

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a167ac8d-9eda-4f18-a13f-854aa4549b93

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}