feat: persist active tab in TabList via URL search param

[fedepini]

Summary

• TabList now persists the active tab in the URL as a search parameter (tab-<uid>)
• The active tab survives page refresh and is shareable via URL
• Tab switches use replace (not push) to avoid polluting browser history
• Existing search params (including widgetEndpoint) are preserved when a tab changes

Implementation

The change is contained entirely in src/widgets/TabList/TabList.tsx:

• useSearchParams reads and writes the active tab key
• The param is namespaced per widget instance (tab-<uid>) so multiple TabLists on the same page don't collide
• Before applying the stored key, it is validated against the current tab items — if the tab no longer exists (e.g. YAML was updated), it silently falls back to tab 0

Behaviour across navigation scenarios

Scenario	What happens
User selects tab 2, then refreshes the page	URL is preserved → lands on tab 2 ✓
User selects tab 2, copies and shares the URL	Recipient lands on tab 2 ✓
User clicks the browser back button after switching tabs	Goes to the previous page, not the previous tab (because tab switches use replace) ✓
Panel click → path navigate to a page containing a TabList	Clean URL, TabList starts at tab 0 (fresh navigation, no prior tab context) ✓
Panel click → resourceRefId navigate on the same page	URL becomes ?widgetEndpoint=<encoded> — tab param stripped, but TabList is not rendered in this state ✓
User navigates away via a nav menu item and comes back via the same item	Fresh URL, tab 0 (expected reset on intentional navigation) ✓
Multiple TabLists on the same page	Each uses its own tab-<uid> param — no collisions ✓
YAML updated and the previously active tab no longer exists	Falls back silently to tab 0 ✓

Test plan

• Open a page with a TabList, switch to a non-default tab, refresh — confirm landing on the same tab
• Open the URL in a second browser tab — confirm both show the same active tab
• Switch tabs several times, press browser back — confirm going to the previous page, not cycling through tab history
• Verify that pages with two or more TabLists persist each independently
• Trigger a navigate action from a widget on the same page — confirm tab param does not interfere

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