feat(seer): Add In Progress tab to autofix overview

[NicoHinderling]

Adds an All Runs / In Progress tab bar to the Autofix overview page (AIML-3324).

What

• A Tabs/TabList bar sits above the run list. In Progress is a pure frontend filter on runs whose live status is processing — no new API calls, no backend change.
• Tab counts (All Runs (N) / In Progress (M)) are derived from the runs already fetched/polled by the overview hook, and respect the active assignee filter so the counts and the visible list always agree.
• The selected tab persists in the URL (?view=in_progress), matching how sort and assignee already work, so the view is shareable.
• Empty In-Progress tab reuses the existing EmptyState with a tab-specific message; empty sections continue to auto-hide.

Notes

• Stacked on feat(seer): Poll live autofix run status on overview #122191 (the live status-poll PR) — it supplies the status field this tab filters on. Merge/deploy order: backend status expand → status-poll frontend → this tab.
• Known limitation: a run only appears in the overview once it has produced a root cause (the endpoint is built from milestone rows). So this tab shows runs the agent is actively advancing between milestones, not brand-new runs still computing their first root cause. Surfacing pre-root-cause runs would need backend work and is out of scope here.
• Counts are exact only while in-progress runs stay under the per-section 100-run cap (true in practice).

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