Persist timeline expand/collapse state in URL

[rawadhossain]

The timeline view's expand/collapse state was not reflected in the URL, making it impossible to share a view showing a specific set of tasks. Recipients would always see the default expanded state instead of what the sharer was viewing.

This PR adds an open_steps query parameter that persists the expand/collapse state of timeline steps in the URL.

Closes #42

Behavior

URL state	Meaning
No open_steps param	All steps expanded (default) — clean URLs
?open_steps=start,end	Only these steps are expanded
?open_steps= (empty)	All steps collapsed

Changes

• useTaskListSettings.ts — Added open_steps as a URL query param via use-query-params. Excluded from custom mode localStorage presets.
• RunPage.tsx — Single useEffect with phase tracking: applies URL state on initial load, syncs state URL on user toggle. Uses replaceIn so expand/collapse actions don't create browser history entries.
• cypress/integration/run_details.js — Extended existing collapse tests with 3 new assertions for open_steps URL behavior.
• PluginRegisterSystem.tsx (additional fix) — Fixed a pre-existing crash when the /plugin API returns a response instead of a plain array. This was blocking local development and was fixed while working on this PR.

Screenshots

Steps collapsed - open_steps param in URL

Steps expanded - param removed from URL

Video Demo

test.mp4

Edge Cases Handled

• Steps that load late are closed if they're not in the URL's open list
• Switching to a different run reset everything cleanly
• All open = no param in URL, all closed = open_steps= (empty), these are treated differently

[Harshil-Malisetty]

nice implementation, I had a similar approach in #184 but I see you used useTaskListSettings which is much cleaner since it follows the existing URL param pattern in the codebase. the Cypress tests is a good call as well