feat(filter): expose branch filters in client surfaces

[prateek]

Adds branch filtering to the session-browsing surfaces. The CLI accepts --branch on session list, session search, and activity report; each requires --project because branch names are project-scoped. MCP tools accept the same human inputs: a plain project plus a plain git_branch. Both surfaces encode the internal (project, branch) token at the edge, so callers never need to see or construct token separators.

On the web, the shared sidebar filter gets a Branch section with multi-select, client-side search, selected branches floated to the top, removable chips, a numeric active-filter badge, and URL round-trip. The same selection flows into Analytics and usage filtering.

Branch metadata now sorts by most recent session activity in SQLite, PostgreSQL, and DuckDB, with project and branch tiebreakers for deterministic lists. cmd/testfixture seeds synthetic branch data so screenshots and e2e fixtures exercise the branch surfaces.

Known limitation: branch filters still travel as an uncapped token list, matching the existing CSV-style filters rather than adding a separate cap in this PR.

Part of #928; parallel to the activity-rollups and usage-grouping PRs.

[roborev-ci]

roborev: Combined Review (1d0d16d)

Summary: Branch filtering is partially wired; URL round-tripping and analytics behavior have medium-severity gaps.

Medium

• Location: frontend/src/lib/stores/sessionRouteParams.ts:6 (also frontend/src/lib/stores/router.svelte.ts:72, frontend/src/lib/components/usage/UsagePage.svelte:174)

  • Problem: filtersToParams now emits git_branch, but the URL allowlists still omit it. Branch-only deep links are ignored, branch-only filter changes may be considered equal and skipped from URL writes, session links can drop the branch param, and Usage page URL init filters it out.
  • Fix: Add git_branch to the shared session filter/route param sets and UsagePage’s supported session param set, with URL round-trip tests.

• Location: frontend/src/lib/components/filters/SessionFilterControl.svelte:396

  • Problem: The shared filter dropdown now exposes Branch on the Analytics page, but AnalyticsStore never syncs sessions.filters.branch or sends gitBranch in analytics requests. Selecting a branch appears active in the filter UI while analytics results remain unfiltered.
  • Fix: Wire branch through Analytics store/page/active filters and include gitBranch in analytics params, or hide the branch section for analytics until supported.

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Reviewers: 2 done | Synthesis: codex, 9s | Total: 10m17s

[roborev-ci]

roborev: Combined Review (9cb8887)

Summary verdict: No Medium, High, or Critical findings to report.

Both reported findings are Low severity, so they are omitted per the requested threshold.

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Reviewers: 2 done | Synthesis: codex, 4s | Total: 6m33s

[prateek]

Addressed the automated review findings: git_branch was missing from the session-param allowlists in sessionRouteParams.ts, router.svelte.ts, and UsagePage.svelte, so a shared URL with a branch filter would drop it on load — all three now include it, with an allowlist test. Also reworded the git_branch row in docs/session-api.md to document the opaque token format (the CLI --branch flag encodes it for you).

[roborev-ci]

roborev: Combined Review (e6138c3)

Reviewed branch-filter changes: no Medium, High, or Critical findings to report.

Only one Low-severity documentation issue was reported, so it is omitted per the requested threshold.

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Reviewers: 2 done | Synthesis: codex, 7s | Total: 10m58s

[wesm]

I'll take a closer look at this. My agentsview archive has thousands of branches so this selector has a lot higher cardinality than any of the other selectors in the project at this point

[roborev-ci]

roborev: Combined Review (d344518)

No issues found.

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Reviewers: 2 done | Synthesis: codex | Total: 11m27s

[wesm]

Took a closer look. In my agentsview database I have 1066 branches — we don't want to stuff this much data into the DOM for the branch selector control on page render so we will need to do some virtualization work cc @mariusvniekerk

[wesm]

superseded by #1017