bugfix: stop highlighting process tool errors

[Grace-dev11]

Summary

• Process tool failures and failed file edits no longer use the red error treatment on the activity timeline.
• Tool error text stays in the existing collapsed detail card, in the same ink as other output. File edits keep a single Failed {filename} row.
• Removes the recovered-retry heuristic, which left unrecovered failures highlighted. Model-unavailable and quota notices stay red.

Test plan

• Run a task whose shell command fails and is not retried successfully. The row stays one ordinary Ran … line, with no red traceback underneath.
• Expand that row and confirm the original error is still in the card, same color as normal output.
• Confirm a failed file edit shows only Failed {filename}, not the error paragraph.
• Confirm model-unavailable and quota-exhausted notices are still red.

Made with Cursor

[Grace-dev11]

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