Fix workbench scenario lifecycle guards

[bnquon]

Summary

• Prevents unsaved drafts from restoring removed imported scenarios.
• Blocks scenario/example actions during file operations and loading.
• Keeps removal and Exit refresh failures visible.
• Preserves the blank workbench, History access, and historical read-only behavior.

Validation

• npm run check
• npm run test:frontend -- --run
• git diff --check

Broad lifecycle/integration coverage remains intentionally deferred. Generated build and mode-only changes were excluded from the commit.

[pullfrog]

Important

This PR leaves an unsynchronized unsaved-scenario refresh path that can report a successful newer operation as a failure and lose a newly saved scenario; please address before merging.

Reviewed changes This review covers scenario lifecycle guards, unsaved and empty-workbench transitions, scenario-browser action gating, and workspace bootstrap result propagation.

• Scenario transitions Tracks the scenario opened before an unsaved draft and adds an Exit action that restores it or refreshes the workspace.
• Empty workbench Adds a blank state when examples are hidden and no local scenario is available, with a restore action.
• Interaction guards Blocks scenario selection, removal, import, and example dismissal during runs, file operations, loading, and historical read-only mode.
• Refresh outcomes Makes workspace bootstrap report success and surfaces removal and Exit refresh failures.
• Save feedback Adds an accessible interactive multiline tooltip explaining why Save as is unavailable.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using GPT Luna ｜ 𝕏}

[pullfrog]

✅ No new issues found.

Reviewed changes This incremental review covers the refresh-race fixes added since the previous Pullfrog review.

• Distinguished refresh outcomes Separated successful, failed, and superseded workspace bootstrap requests so stale results do not surface as failures.
• Serialized unsaved exits Prevented repeated Exit refreshes and ignored superseded results during unsaved-scenario recovery.
• Extended lifecycle guards Propagated catalog-loading state to Save as and scenario browser actions, and handled superseded removal refreshes without reporting false failures.

  ^{｜ View workflow run ｜ Using GPT Luna ｜ 𝕏}