fix(desktop): stop idle goal runs

[cyq1017]

Summary

• stop an idle active goal when Cancel has no foreground turn cancel function
• clear the active goal from the desktop Stop button while goal mode is active
• add backend and Composer regressions for stopping a goal/todo run

Fixes #5200.

Tests

• go test ./internal/control -run 'TestCancelStopsIdleGoalWithIncompleteTodos|TestCancelClearsPendingApprovalRuntimeStatus|TestCancelClearsPendingAskRuntimeStatus|TestGoalCommandAutoContinuesUntilComplete|TestGoalModeSkipsAutoPlanApproval|TestGoalInterceptsCompleteWithIncompleteTodos' -count=1\n- npx pnpm@10 exec tsx src/tests/composer-goal-toggle.test.tsx\n- go test . -count=1 (desktop)\n- npx pnpm@10 run test:all (desktop/frontend)\n- go test ./... -count=1\n- git diff --check HEAD~1..HEAD\n

[SivanCola]

Closing this as superseded by the merged integration PR #5512.

What was kept/adapted:

• The idle active-goal Stop behavior and Composer goal-clear path from this PR were adapted in Fix desktop long-history lag and cancellation state / 修复桌面端长历史卡顿与取消状态 #5512.
• Fix desktop long-history lag and cancellation state / 修复桌面端长历史卡顿与取消状态 #5512 includes backend and frontend regression coverage for the goal/todo Stop path.

Attribution:

• @cyq1017 is credited in Fix desktop long-history lag and cancellation state / 修复桌面端长历史卡顿与取消状态 #5512's consolidation notes and repository contributor credits.

Verification:

• Fix desktop long-history lag and cancellation state / 修复桌面端长历史卡顿与取消状态 #5512 is merged and its GitHub checks are green, including cache-impact, desktop, lint, race, coverage, CodeQL, and ubuntu/macos/windows tests.