fix(chat): increment temp file suffix correctly

[xxynet]

⚠️ Base branch must be dev. PRs targeting main will be rejected.

Summary

Fix temp-file collision numbering so repeated downloads keep a stable basename and increment numerically instead of accumulating suffixes such as _1_2_3.

Type of change

• feat: New feature
• fix: Bug fix
• refactor: Code refactor (no functional change)
• docs: Documentation update
• chore: Build, CI, dependencies, or other maintenance
• style: Code style / formatting (no logic change)
• test: Adding or updating tests

Changes

• Keep the original destination root and extension fixed while _move_no_clobber searches for an available numbered path.
• Add a regression test covering collisions with both the base destination and its first numbered fallback while preserving existing file contents.

Screenshots / Logs

python -m pytest tests/ -q
575 passed, 1 skipped, 2 warnings in 29.68s

Checklist

• I have tested these changes locally
• I have updated documentation if needed
• New dependencies have been added to requirements.txt (if applicable)
• If this PR introduces new features, they have been discussed with the owner or maintainer
• This PR does not introduce breaking changes

Summary by CodeRabbit

• Bug Fixes

  • File moves now consistently select the next available numbered filename when multiple matching files already exist.
  • Existing files remain unchanged, while the source file is moved successfully.

• Tests

  • Added coverage for filename selection when the original and first numbered filenames are already present.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: 2004eea2-3eb7-4233-96ad-2ba23eeed55f

📥 Commits

Reviewing files that changed from the base of the PR and between 5d6c9a7 and 78195ee.

📒 Files selected for processing (2)

• core/chat/message_elements.py
• tests/test_message_elements.py

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The move helper now derives numbered fallback names once from the original candidate path. A regression test verifies that existing candidates remain unchanged and the source moves to the next available name.

Changes

Non-clobbering file move

Layer / File(s)	Summary
Move retry and regression coverage core/chat/message_elements.py, tests/test_message_elements.py	_move_no_clobber computes the candidate root and extension before the retry loop. The test verifies that the source moves to download_2.png while existing files remain unchanged.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 78195

Downloads now retain a stable basename and select the next numbered filename without overwriting existing files. The change is ready to merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: correcting temporary-file suffix increments in chat downloads.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

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• Create a new PR

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_{A rabbit checks each filename twice
Existing bytes stay snug and nice
The source hops to number two
No clobbering breaks the queue
Tests guard the burrow too}

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