💡 Change Scope

• Small Change: Fast feedback, localized UI/logic, low-risk.
• Large Change: New feature, cross-boundary logic, runtime-risk (persistence, IPC, lifecycle, recovery).

📝 What Does This PR Do?

Fixes the renderer crash that could happen while dragging a task/node when the embedded terminal renderer is transiently detached.

This branch also hardens the regression coverage around the same canvas interaction surface:

• keeps the detached-renderer drag crash locked down on the real user path
• swaps the flaky arrange-in-space keep-fit warning case to a deterministic test harness path
• moves the space-owned node resize expansion assertion to a deterministic unit regression around the layout owner

🏗️ Large Change Spec (Required if "Large Change" is checked)

1. Context & Business Logic

Dragging a canvas task can temporarily detach the xterm renderer subtree while drag/geometry synchronization is still flushing. The renderer must treat that detach as a harmless transient state instead of trying to reconcile against a missing renderer and crashing the React tree. The surrounding canvas regression coverage also needs to stay stable enough for pnpm pre-commit to prove the bug stays fixed.

2. State Ownership & Invariants

• Terminal runtime owns renderer attachment state; drag-time sync must not force renderer work after the renderer becomes detached.
• Arrange-in-space with spaceFit=keep must remain side-effect free when there is not enough room.
• Space-owned node resize layout must keep owned nodes enclosed while keeping root windows non-overlapping.

3. Verification Plan & Regression Layer

• pnpm pre-commit (exit 0)
• pnpm exec playwright test tests/e2e/workspace-canvas.arrange.space.spec.ts --project electron --reporter=line -g "warns and keeps layout unchanged when arrange-in-space keep-fit has no room" --repeat-each=8
• pnpm test -- --run tests/unit/contexts/workspaceCanvasNodeResizeLayout.spec.ts

✅ Delivery & Compliance Checklist

• My code passes the ultimate gatekeeper: pnpm pre-commit is completely green.
• I have signed the CLA if required (see CLA.md).
• I have included new tests to lock down the behavior (or explicitly stated why it's untestable).
• I have strictly adhered to the DEVELOPMENT.md architectural boundaries.
• I have attached a screenshot or screen recording (if this touches the UI).
• I have updated the documentation accordingly (if adding a feature or changing a contract).

📸 Screenshots / Visual Evidence

Not attached from CLI. Regression proof is covered by Playwright + unit tests in this branch.