Render standalone entity stream errors

[KyleAMathews]

Summary

• include standalone entity stream errors in the main timeline query
• render errors with their error code and message in the timeline UI
• keep existing run-attached error/fallback rendering unchanged

Verification

• pnpm --dir packages/agents-server-ui typecheck
• pnpm --dir packages/agents-runtime test entity-timeline --run

Note: full packages/agents-runtime typecheck still fails on existing unrelated missing exports in test/pg-sync-source.test.ts.

[github-actions]

Electric Agents Desktop Builds

Build artifacts for commit 8cb86cb.

Platform	Status	Artifact
macOS Apple Silicon	Passed	DMG
macOS Intel	Passed	DMG
Windows x64	Passed	Installer
Linux x64	Passed	AppImage / deb

Workflow run

[codecov]

Codecov Report

❌ Patch coverage is 0% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.74%. Comparing base (916f6cd) to head (8cb86cb).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
packages/agents-runtime/src/entity-timeline.ts	0.00%	25 Missing ⚠️
...agents-server-ui/src/components/EntityTimeline.tsx	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4547      +/-   ##
==========================================
- Coverage   54.80%   54.74%   -0.07%     
==========================================
  Files         317      317              
  Lines       36681    36709      +28     
  Branches    10466    10469       +3     
==========================================
- Hits        20104    20097       -7     
- Misses      16544    16579      +35     
  Partials       33       33              

Flag	Coverage Δ
packages/agents	70.53% <ø> (ø)
packages/agents-mobile	71.42% <ø> (ø)
packages/agents-runtime	80.08% <0.00%> (-0.17%)	⬇️
packages/agents-server	73.98% <ø> (+0.02%)	⬆️
packages/agents-server-ui	5.67% <0.00%> (-0.01%)	⬇️
packages/electric-ax	46.42% <ø> (ø)
typescript	54.74% <0.00%> (-0.07%)	⬇️
unit-tests	54.74% <0.00%> (-0.07%)	⬇️

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[github-actions]

Electric Agents Mobile Build

Local mobile checks ran for commit 8cb86cb.

The EAS Android preview build was skipped because the mobile-eas-build label is not present.
Add the mobile-eas-build label to this PR to produce an installable preview build.

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