Fix checkpoints not appearing in chat when metadata is invalid

[roomote]

Fixes #5899

Problem

Users reported that checkpoints are not appearing in the chat despite having checkpoints enabled in settings. Investigation revealed that the CheckpointSaved component was returning null when checkpoint metadata failed schema validation, causing checkpoints to be completely hidden from the UI.

Root Cause

The CheckpointSaved component was too strict in its validation - if the checkpoint metadata did not exactly match the expected schema, the entire checkpoint display would be hidden by returning null.

Solution

Modified the CheckpointSaved component to:

1. Always show checkpoints: Instead of returning null for invalid metadata, show a fallback display
2. Add debugging support: Console warnings are logged when metadata is missing or invalid to help diagnose issues
3. Graceful degradation: When metadata is invalid, use sensible defaults while still showing the checkpoint
4. User feedback: Display a subtle "metadata unavailable" indicator when using fallback data

Changes

• Modified webview-ui/src/components/chat/checkpoints/CheckpointSaved.tsx:
  • Added console warnings for debugging metadata issues
  • Created fallback metadata when validation fails
  • Always render checkpoint display instead of returning null
  • Added visual indicator when metadata is unavailable

Testing

The fix ensures that:

• Checkpoints with valid metadata continue to work as before
• Checkpoints with invalid/missing metadata are still visible to users
• Developers can debug metadata issues via console warnings
• The CheckpointMenu functionality remains intact with fallback data

This change prioritizes user experience by ensuring checkpoints are always visible, while providing debugging tools for developers to identify and fix underlying metadata issues.

---

Important

Fix CheckpointSaved to always display checkpoints with fallback data and log warnings for invalid metadata.

• Behavior:
  • CheckpointSaved component now always displays checkpoints, even with invalid metadata, using fallback data.
  • Logs console warnings for missing or invalid metadata for debugging.
  • Displays a subtle indicator when metadata is unavailable.
• Changes:
  • Modified CheckpointSaved.tsx to use fallback metadata when validation fails.
  • Added console warnings for metadata issues in CheckpointSaved.tsx.
  • Updated rendering logic to ensure checkpoints are always visible.

^{This description was created by for 1342a1e. You can customize this summary. It will automatically update as commits are pushed.}

[ellipsis-dev]

Avoid providing an inline English fallback string in the translation call. Remove the second argument from t('chat:checkpoint.metadataUnavailable') and manage defaults via the translation JSON files.

Suggested change

	{t("chat:checkpoint.metadataUnavailable", "metadata unavailable")}
	{t("chat:checkpoint.metadataUnavailable")}

^{This comment was generated because it violated a code review rule: irule_C0ez7Rji6ANcGkkX.}

[daniel-lxs]

@roomote-agent use the switch_mode tool to switch to pr-fixer mode and address the comment left by ellipsis-bot on this PR, do not create a new PR

[roomote]

👋 I've received your request and switched to pr-fixer mode. I can see the ellipsis-bot comment about removing the inline English fallback string from the translation call. I'll address this issue now.