Project filter selections now apply instantly

Filter combobox selections and status age inputs reflect your choices immediately instead of flashing back while the URL updates.

Bug Fixes

Filter selections on the global project list now respond instantly with optimistic UI updates, eliminating the visual flicker where inputs would revert to their previous value while the URL was updating. The branch filter clear now correctly defaults to "All Branches" instead of bouncing back to the active branch. The search input also received a cosmetic fix: it no longer reserves space for a spinner when idle, which was truncating the placeholder text. We've widened the search field from 144px to 192px to comfortably fit "Search projects…".