Fix desktop long-history lag and cancellation state / 修复桌面端长历史卡顿与取消状态

[SivanCola]

Summary

• Add paged desktop history APIs so long-session hydration loads the latest visible user-turn window first and fetches older history on demand.
• Keep and extend the cached-transcript reuse path from fix(desktop): skip cached transcript history reloads #5495, including the session identity guard, so repeat tab/topic opens do not reload the same transcript.
• Avoid full-history checkpoint refreshes after turn_done, move BalanceForTab out of the blocking hydrate path, and coalesce transcript resize repinning into animation frames.
• Return an explicit cancelled shell tool result for desktop RunShell cancellation so Stop can reconcile the foreground turn cleanly.
• Run foreground/background shell processes through the existing tracked process-tree runner where cleanup is required, so Windows bash/PowerShell child processes are assigned to a Job Object and reaped on cancel, timeout, or normal shell exit.
• Stop idle active goal/todo runs when Desktop Stop has no foreground turn to cancel, and clear the active goal from the Composer Stop path.
• Preserve the real user prompt on explicit cancellation while stripping partial assistant/tool/todo remnants, so follow-up turns and resumes do not lose user context after Ctrl+C.
• Persist an in-flight turn marker in session sidecar metadata and clear stale partial assistant/tool/todo tails on resume after a force quit, crash, or kill during a turn.

Fixes #5306
Fixes #5200
Fixes #5499
Fixes #4986
Refs #5355
Refs #5495
Refs #5210

Consolidation notes

Kept/adapted:

• fix(desktop): skip cached transcript history reloads #5495 by @GTC2080: keeps the cached transcript skip and sessionPath identity guard, then extends the same hydration flow to use paged history instead of all-history reloads.
• fix(desktop): stop idle goal runs #5210 by @cyq1017: reimplements the idle active-goal Stop behavior and Composer goal clear on this branch, with backend and frontend regressions.
• fix(desktop): paginate restored transcript warm turns #5355 by @GTC2080: this PR builds on the merged transcript warm/cold rendering fix; it does not duplicate that rendering-window work.

Reviewed but not adopted:

• perf(desktop): wrap Transcript in React.memo to prevent IME input lag #4331 by @weikejia123: targets parent rerender/IME lag by memoizing Transcript; this PR focuses on the long-history hydrate payload and reducer path.
• perf(cross-layer): three-batch performance refactoring for TUI, Desktop, Provider & EventWire layers #5434 by @ADX15xs: broad cross-layer performance refactor touching provider/eventwire/CLI/Desktop code; this PR stays scoped to desktop history hydration, resize coalescing, shell process-tree cancellation, and cancellation-state cleanup.

Repository Contributor Credits

• @GTC2080 contributed the fix(desktop): paginate restored transcript warm turns #5355 transcript warm/cold rendering fix and the fix(desktop): skip cached transcript history reloads #5495 cached-transcript reload analysis/implementation direction that this PR keeps and extends.
• @cyq1017 contributed fix(desktop): stop idle goal runs #5210's idle goal/todo cancellation direction; this PR adapts that behavior on the consolidated branch.
• @weikejia123 contributed perf(desktop): wrap Transcript in React.memo to prevent IME input lag #4331's alternative Transcript memoization investigation, reviewed here as an adjacent performance approach.
• @ADX15xs contributed perf(cross-layer): three-batch performance refactoring for TUI, Desktop, Provider & EventWire layers #5434's broader performance-refactor exploration, reviewed here as an adjacent but out-of-scope approach.

Cache impact

Cache-impact: none for provider prompt caching. This changes desktop/Wails history hydration, frontend state handling, controller shell cancellation, shell process-tree cleanup, idle-goal cancellation, post-cancel transcript cleanup, and session sidecar recovery metadata; it does not change system prompts, provider request serialization, tool schemas, memory prefixes, or compaction behavior.
Cache-guard: N/A for provider cache; focused desktop/frontend and Go tests are listed below.
System-prompt-review: N/A.

Verification

• PASS git diff --check origin/main-v2...HEAD
• PASS go test ./...
• PASS go test ./internal/control
• PASS go test ./internal/agent
• PASS go test ./internal/tool/builtin
• PASS go test ./internal/proc
• PASS go test ./internal/agent -run 'TestSessionInFlightTurnMetaRoundTrip|TestRunCancelledMidStreamLeavesResumableSession|TestCancelDuring(StuckProviderStreamReturnsPromptly|ToolExecutionBreaksOutPromptly|BatchStopsRemainingTools)|TestCancelBeforeParallelBatchSkipsTheWholeRemainingBatch|TestCancelInsideLargeParallelBatchStopsSchedulingNewTools'
• PASS go test ./internal/control -run 'TestResumeClearsStale(Visible|Synthetic)InFlightTurn|TestTurnOrchestratorCancelPreservesVisibleUserPrompt|TestTurnOrchestratorCancelFlushesCleanTranscriptToDisk|TestCancelStopsIdleGoalWithIncompleteTodos|TestRunShell_CancelStopsCommand'
• PASS go test ./internal/tool/builtin -run 'TestBash(CancelReturnsPromptly|ForegroundTimeoutConfig|ExplicitZeroTimeoutDoesNotCapForeground)|TestWorkspacePassesBashTimeout|TestShouldReapAfterRunHonorsExplicitPreserveOnlyOnCompletion|TestReapTreeKillsBackgroundProcess|TestBackgroundKill'
• PASS GOOS=windows GOARCH=amd64 go test -c ./internal/tool/builtin
• PASS GOOS=windows GOARCH=amd64 go test -c ./internal/proc
• PASS go test . -run 'TestHistory(Page|Checkpoint|Preview|Resume)' from the desktop module
• PASS pnpm --dir desktop/frontend typecheck
• PASS pnpm --dir desktop/frontend check:css
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/composer-goal-toggle.test.tsx
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/use-controller-meta.test.ts
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/tab-switch-hydration.test.tsx
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/new-session-load-race.test.tsx
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/use-controller-cancel-reconcile.test.tsx
• PASS pnpm --dir desktop/frontend exec tsx src/__tests__/resize-drag.test.ts