feat(web): group, filter and sort the sidebar inbox

The sidebar inbox is one flat list. With several environments, projects
and providers in play there is no way to see "just this machine" or
"just Codex" without scoping to a single project at a time, and every
card repeats the project name whether or not that is the useful bit.

Adds a compact bar under the project selector with three menus:

- Group by: environment, project or provider, plus an optional second
  axis nested inside the first. "Nothing" keeps today's flat list and
  stays the default.
- Provider filter: narrows every shelf, not just the inbox, so the
  filter never lies about what "only Claude" means.
- Sort: last activity or date created. The existing project grouping
  mode (repository / folder / project) is surfaced here too, instead of
  living only in Settings.

Each trigger reads out its current choice, so the bar doubles as the
readout of how the list is arranged.

Grouped rows say each thing once: a card drops whatever a section header
above it already states, so the same row is three lines in the flat list
and one line under a project header. Collapsed sections carry an
attention rollup — approvals, input requests, failures, unread
completions and running work — using the same status rules the rows
themselves follow, so a header can never claim something its rows would
not show. Unread finished threads get a dot next to their title.

The grouping itself is pure and unit-tested: sections come out in
first-appearance order and threads keep their incoming order, so sorting
and grouping stay orthogonal. Collapse state persists per section key
and resets when the axes change, so stale keys cannot pre-collapse
unrelated sections. Pinned keeps its manual order and the snoozed and
settled shelves stay whole.

Written by Claude Opus 5 in Claude Code.

Author: BarretoDiego