feat(console/list-pages): persist selected item id in URL

[vaderyang]

Summary

Agent Turns, LLM Calls, and HTTP Exchanges keep the slide-over detail's open id in React state, so copying the URL or hitting refresh drops the selection and reopens the list with no panel. Every other filter on those pages already round-trips through the URL via `useSearchParamState`; this is the one holdout.

Move the selected id onto a `?selected=` query param backed by the same hook. Now:

• Copy URL lands a recipient on the same row with the panel open.
• Refresh / back-forward restores the panel.
• Close panel removes the param (empty string is the default → the hook drops the key).

Implementation detail

LLM Calls and HTTP Exchanges also tracked `selectedIndex` (for the panel's prev/next buttons). That state was redundant — the index is now derived from `items.findIndex(i => i.id === selectedId)`. One source of truth (the URL); prev/next still works as long as the selected id is on the current page.

If the URL points to an id that isn't on the visible page (e.g. someone pasted a link with a different filter or stale time range), the prev/next buttons naturally disable (`index = -1`) but the detail still loads — the panel queries by id rather than indexing into the list.

Verification

• `bun test` — 97 pass
• `npm run build` — green
• Deployed to wuneng (new bundle index-_yoJkBO2.js); panel opens / closes / survives refresh on all three pages

Test plan

• Open a row in Agent Turns → URL gains `?selected=<turn_id>`
• Copy URL into a new tab → list opens with that row's detail panel
• Refresh while the panel is open → panel stays open on the same row
• Close the panel → `selected` param disappears from the URL
• Same flow on LLM Calls and HTTP Exchanges
• On LLM Calls, prev/next buttons still work; disable correctly at edges

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