fix: stop showing timers as pending after workflow cancellation

[ItsRoy69]

Fixes #3156

When a workflow is cancelled, timers from the try block that haven't
received TimerFired or TimerCanceled events continue to display as
pending in the UI — the timeline shows a ticking line extending rightward
and the event table shows them as active, even though the workflow has
moved to executing the cancellation handler.

• Manual testing
• E2E tests added
• Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

• Go to http://localhost:3000/namespaces/default/workflows
• Click on timer-cancel-test

Event History with Yellow/canceled background
Timeline tab with Short segment, no pending dashes
Timer Status with Shows as Canceled
10s cleanup timer appears separately, runs normally

Issue(s) closed #3156

[vercel]

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