fix(replay): keep route transitions from blocking capture work

[Chinmay-KB]

Summary

Route animations no longer freeze Tugboat's serialized event pipeline. Pointer, lifecycle, and cancellation work can continue while a transition deadline is pending; only the destination capture and route finalization enter the queue when that deadline is ready.

Obsolete route timers and capture waiters are now cancellable across supersession, backgrounding, disposal, session end, and session replacement. Capture-generation and session-identity fences prevent an already-running stale screenshot from publishing into a replacement session.

This PR is stacked on #15 so the deterministic replay-coherence harness is available to prove the runtime behavior.

Related: #6

Validation

• flutter analyze — clean
• flutter test — 169 tests passed
• The new deterministic cases cover queue progress during a transition, supersession, lifecycle/session cancellation, blocked and failed captures, and late-frame rejection.
• Existing observer-backed navigation tests, including push-and-remove stack cleanup with a non-zero transition, remain green.

Fixes #6.

[Copilot]

Pull request overview

This PR refactors Tugboat’s replay controller route handling so Navigator transition delays no longer occupy the serialized controller queue, allowing pointer/lifecycle/cancellation work to continue while a route deadline is pending.

Changes:

• Move route transition + settle waiting out of the controller’s serialized queue, enqueueing only the final route capture/finalization once the deadline is reached.
• Add cancellable route-deadline and capture waiters, plus generation/session fences to prevent stale capture output from publishing after supersession/session replacement.
• Extend deterministic replay coherence characterization tests to cover queue progress, supersession, lifecycle/session cancellation, and capture failure paths; bump SDK version to 0.4.2.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/tugboat/lib/src/controller.dart	Implements deferred (out-of-queue) route deadlines, cancellable waiters, and stale-capture fences.
packages/tugboat/test/helpers/replay_coherence_harness.dart	Adds a cancellable deterministic scheduler seam to drive the new deadline behavior in tests.
packages/tugboat/test/replay_coherence_characterization_test.dart	Adds deterministic coverage for non-blocking transition deadlines and cancellation/supersession scenarios.
packages/tugboat/pubspec.yaml	Version bump to 0.4.2.
packages/tugboat/lib/src/sdk_version.dart	Keeps SDK version constant in sync with pubspec.yaml.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.