Show failed file-tool errors on the collapsed transcript line

[TheGreatAxios]

Summary

Failed read_file (and equivalent file-tool) rows show the error text on the collapsed transcript line, not only a failure mark. Success rows are unchanged.

Without the error, a missing tool-output:// blob or missing path looks like a wedged session: the tool failed, the operator cannot see why, and the model retries the same URI.

• The collapsed line surfaces the same model-visible error payload (flattened to the log-preview budget when long).
• Missing blob URI and missing filesystem path both render the error plus the path subject and ×.
• Success read_file still shows the path and ✓, not the file body.

Verification

• bun run typecheck, bun run build, and bun run test pass
• bun run check passes
• bun test src/tui/tool-rows.test.ts covers missing blob, missing file, and unchanged success rows

Fixes CL-7621

[linear-code]

CL-7621

[TheGreatAxios]

Critic · Comment

Failed file-tool rows put the tool-result error on the collapsed transcript line; success rows stay path plus mark.

Findings

No findings.

Notes

Merge-ready against CL-7621. resultAddendum now forwards result.text (abbreviated) onto stat, which toolSentenceLines already paints. The two missing-file cases and the success-row case are covered in src/tui/tool-rows.test.ts.