feat: Add busy-stall focus rescue and richer server_busy / compile guidance

[hatayama]

Summary

• B-7a: When server_busy retries persist for 5s within the 10s busy retry window, focus Unity once via connectionRetryFocusController (busy_stall) and restore focus on exit.
• B-7b: Enrich UNITY_SERVER_BUSY CLI errors with EditorActivity (compile/import/play state when true) and contextual NextActions.
• B-8: When compile fails on externally changed Scene files (resolve/reload/save failure messages), add NextActions with an execute-dynamic-code EditorSceneManager.OpenScene example and unsaved-change guidance.

Pre-implementation verification (new protocol)

B-7a — busy path focus rescue repro (TDD Red → Green)

• Root cause (pre-fix): busy retry loop never called focusController.tryFocus; terminal focus path also skips server_busy.
• TDD repro: TestSendWithTransientConnectionRetryFocusesOnceAfterPersistentBusy was Red on pre-fix code (focusCallCount stayed 0).
• Production tuning: finishBusyRetry bounds busy retries to serverConnectionRetryDefaultTimeout (10s), so the stall threshold must stay below that window. Default is 5s (focus at 5s, ~5s retry remaining). TestDefaultBusyFocusStallThresholdFitsWithinBusyRetryWindow guards this ratio.

B-7b — discriminable Unity states on server_busy

Field	Source	Included?
isCompiling	EditorApplication.isCompiling via EditorRuntimeStateService	Yes
isUpdating	EditorApplication.isUpdating	Yes
isPlaying / isPaused	existing play state	Yes
secondsSinceLastMainThreadTick	EditorMainThreadLivenessTracker	Yes (existing)
isDomainReloadInProgress	only on compile-status bridge, not server_busy path	Not added

B-8 — external Scene error wording (source-backed)

ExternalSceneChangeResolver.cs messages containing "externally changed Scene files":

• CreateUnresolvedMessage (line 124)
• CreateReloadFailureMessage (line 132)
• CreateDirtySaveBeforeReloadFailureMessage (line 140)

These occur after auto save/reload attempts fail (default path without --stop-on-external-scene-changes). CreateStoppedMessage (line 116) uses different wording and does not match the NextActions gate.

NextActions[1] advises on unsaved in-editor conflicts (not a misleading --stop-on-external-scene-changes rerun hint).

Fable review fixes (bc20a6d)

1. B-7a threshold: defaultBusyFocusStallThreshold 30s → 5s; constant regression test added.
2. B-8 NextActions[1]: removed incorrect auto-reload flag advice; added unsaved-change decision guidance; OpenScene example notes Single discards unsaved editor changes.
3. Editor readiness policy: pass editorState.IsCompiling / IsUpdating through without mutual-exclusion literals.

Verification

• scripts/check-go-cli.sh pass (includes TestDefaultBusyFocusStallThresholdFitsWithinBusyRetryWindow + busy-stall focus test)
• dist/darwin-arm64/uloop compile — 0 errors / 0 warnings
• CompileResponseFactoryTests + ToolExecutionEditorReadyPolicyTests — 13 passed

Release triggers

• cli/common touched with project-runner + dispatcher companions; scripts/stamp-release-inputs.sh run in prior commit.
• No IPC protocol version bump.

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: a0c253d1-f2a3-405e-b4aa-130ddf0c02b3

📥 Commits

Reviewing files that changed from the base of the PR and between 76d4565 and bc20a6d.

📒 Files selected for processing (19)

• Assets/Tests/Editor/CompileResponseFactoryTests.cs
• Assets/Tests/Editor/ToolExecutionEditorReadyPolicyTests.cs
• Packages/src/Editor/Application/UnityCliLoopEditorStateGuard.cs
• Packages/src/Editor/Application/UnityCliLoopToolBusyException.cs
• Packages/src/Editor/Application/UnityCliLoopToolExecutionService.cs
• Packages/src/Editor/Domain/ToolExecutionEditorReadyPolicy.cs
• Packages/src/Editor/FirstPartyTools/Compile/CompileResponse.cs
• Packages/src/Editor/FirstPartyTools/Compile/CompileResponseFactory.cs
• Packages/src/Editor/Infrastructure/Api/JsonRpcResponseFactory.cs
• Packages/src/Editor/Infrastructure/Api/ServerBusyErrorData.cs
• cli/common/errors/busy_editor_state.go
• cli/common/errors/busy_editor_state_test.go
• cli/common/errors/error_envelope.go
• cli/common/errors/error_envelope_test.go
• cli/dispatcher/internal/dispatcher/error_envelope_test.go
• cli/dispatcher/shared-inputs-stamp.json
• cli/project-runner/internal/projectrunner/connection_retry.go
• cli/project-runner/internal/projectrunner/connection_retry_test.go
• cli/project-runner/shared-inputs-stamp.json

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/cli-ux-busy-scene-guidance

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