Fix Agents Window cancellation log noise

[Paul (pwang347)]

Fixes #334441

Summary

• stop accepting customization bundles after disposal, cancel queued filesystem work without executing it, and normalize late provider failures as cancellation
• let already-started filesystem operations settle safely and serialize same-authority bundles so stale scopes cannot overwrite replacements
• resolve optional plugin customization directories without logging expected missing-file stack traces
• log canceled requests at trace level, propagate task-discovery cancellation, and prevent the Agents Window contribution from turning it back into a warning
• add focused regression coverage across bundling, plugin expansion, request logging, and cloud task discovery

Validation

End to end

• Reproduced before the fix in a launched Agents Window by rapidly switching between completed sessions with different working directories: 5 Object has been disposed bundler errors were written to the Window log.
• Repeated the flow against the exact final build with trace logging using 25 cycles / 50 session switches. The final session finished loading, the Window log contained 863 trace entries, and there were 0 matches for disposal errors, failed skill-stat traces, optional plugin EntryNotFound traces, canceled /agents/tasks network errors, or Cloud Sandbox cancellation warnings.

Automated

• ./scripts/test.sh over all five affected suites: 101 passing
• npm run typecheck-client
• targeted ESLint for all changed files
• npm run valid-layers-check
• npm run hygiene
• npm run transpile-client

[Copilot]

Copilot review overview

🟢 Approval recommended

The reviewed changes have regression coverage and no unresolved approval-blocking issues.

Review tier: Balanced
Findings: None

What changed in this PR

Fixes customization bundling races during scope disposal and replacement.

Changes:

• Treats stale bundle work as cancellation.
• Safely drains queued filesystem operations.
• Serializes bundles sharing an authority.
• Adds regression coverage.

File	Description
src/​vs/​workbench/​contrib/​chat/​browser/​agentSessions/​agentHost/​syncedCustomizationBundler.ts	Adds cancellation-aware disposal, queue draining, and authority sequencing.
src/​vs/​workbench/​contrib/​chat/​test/​browser/​agentSessions/​syncedCustomizationBundler.test.ts	Covers queued disposal and same-authority replacement races.

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