refactor(tools): fold background jobs into executeCommand

[zhanba]

Summary

• Add a background flag to executeCommand and remove the standalone startBackgroundJob / readBackgroundJobOutput tools. A background call starts the job and returns its ID plus the output file path, which the model reads with readFile; killBackgroundJob still stops it.
• Wire the flag through all three hosts: VS Code creates a TerminalJob, the CLI delegates to the background job manager, and the WebUI renders background commands via BackgroundJobPanel (job ID travels in output._meta, stripped before reaching the LLM).
• Update tool policies, batching, readonly constraints, fork-task rewriting, settings/stories, browser agent prompt, and custom-agent docs to the single executeCommand surface — startBackgroundJob(...) policy entries are gone, so background commands are governed by executeCommand(...) patterns.

Test plan

• bun check
• bun tsc
• bun run test (includes new packages/tools and updated CLI/VS Code/WebUI tests)
• Manual: run a background command in VS Code, confirm the tool card shows the job, output file is readable with readFile, and killBackgroundJob stops it
• Manual: run a background command in the CLI and confirm the "Running in background" renderer line and output file
• Manual: verify a custom agent restricted with executeCommand(npm run dev) can start that background command and is blocked from others

🤖 Generated with Pochi | Task

[codecov-commenter]

Codecov Report

❌ Patch coverage is 54.74860% with 81 lines in your changes missing coverage. Please review.
✅ Project coverage is 30.62%. Comparing base (a5c28be) to head (93d81b7).

Files with missing lines	Patch %	Lines
.../src/features/tools/components/execute-command.tsx	6.89%	27 Missing ⚠️
...eatures/tools/__stories__/tool-gallery.stories.tsx	0.00%	19 Missing ⚠️
...c/features/chat/lib/use-background-job-display.tsx	0.00%	9 Missing ⚠️
packages/tools/src/utils/tool-batch.ts	22.22%	7 Missing ⚠️
...i/src/features/tools/components/tool-call-lite.tsx	28.57%	5 Missing ⚠️
packages/cli/src/tools/execute-command.ts	87.50%	2 Missing ⚠️
...rc/features/chat/lib/batched-tool-call-adapters.ts	0.00%	2 Missing ⚠️
...ebui/src/features/chat/lib/tool-call-life-cycle.ts	0.00%	2 Missing ⚠️
...scode-webui/src/lib/vscode-running-task-adaptor.ts	0.00%	2 Missing ⚠️
packages/vscode/src/tools/execute-command.ts	93.75%	2 Missing ⚠️
... and 4 more

❌ Your patch status has failed because the patch coverage (54.74%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1892      +/-   ##
==========================================
- Coverage   36.43%   30.62%   -5.81%     
==========================================
  Files         775      770       -5     
  Lines       81332    81084     -248     
  Branches     3646     4128     +482     
==========================================
- Hits        29630    24831    -4799     
- Misses      51589    56135    +4546     
- Partials      113      118       +5     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-08-13 09:10 UTC