fix(vscode): complete slash commands with tab

[ousamabenyounes]

Fixes #2295.

Summary

• make Tab complete the selected slash command into the VS Code chat input instead of sending it immediately
• keep the existing Enter and mouse-click send behavior unchanged
• preserve text around the active token, normalize the argument separator, and place the caret ready for arguments
• add regression coverage for key dispatch, suffix handling, and caret placement

Test verification (RED → GREEN)

• RED: the new completion test initially failed because the insertion helper did not exist
• GREEN: the targeted completion suite passes all 4 tests
• full local suite: monorepo lint (0 errors; existing warnings only), typecheck, and production build passed
• full monorepo tests with bounded concurrency: 1,035 files passed, 16,894 tests passed, 3 expected failures, 83 skipped, 2 todo
• independent code review: PASS after fixing Enter/click compatibility and separator handling

AI assistance disclosure

This patch and PR text were AI-assisted using OpenAI Codex. The implementation was exercised with targeted regression tests and the complete local validation suite; the human contributor remains responsible for reviewing and understanding the submitted changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 901787d

The changes in this PR will be included in the next version bump.

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kimi-code	Patch

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