feat(ui): add session activity receipts and shared overflow

[GCWing]

Summary

• Persist compact session activity summaries and completion receipts across runtime, desktop, Web UI, and CLI peer surfaces.
• Surface consistent running, attention, and completion state in session navigation while preserving independent metadata writers and upgrade-compatible defaults.
• Replace the file-only mention picker with the unified context picker, standardize single-line overflow through the shared design-system primitive, and refresh generated brand assets.
• Restore appearance, design-system registry, review-platform, and affected test compatibility after rebasing onto current main.

Type and Areas

Type: Feature / UI/UX / regression fix / test

Areas: Rust core, session persistence, desktop/Tauri, CLI peer host, Web UI, design system, mobile/installer brand assets, i18n, architecture docs

Motivation / Impact

Session rows can now retain and reconcile durable activity/completion information instead of relying only on attached in-memory UI state. Users get clearer navigation feedback for running, paused, attention-required, and completed work. Text clipping and context selection now follow shared interaction contracts across product surfaces.

Verification

Passed:

• pnpm run check:web
• pnpm run lint:web (0 errors; 11 existing warnings)
• pnpm run design-system:check (UI 249/249, Design Lab 60/60, package contracts, build, typography audit)
• pnpm --dir src/web-ui exec vitest run '--maxWorkers=25%' <39 changed test files> (39/39 files, 663/663 tests)
• pnpm run capabilities:check (22 features, 21 settings, 666 Tauri commands)
• pnpm run check:repo-hygiene
• pnpm run i18n:audit
• git diff --check origin/main
• cargo test -p openbitfun-services-core --test session_contracts (21/21)
• cargo test -p openbitfun-services-core --lib activity_selection_needs_only_metadata_and_leaves_transcripts_unloaded (1/1)
• cargo test -p openbitfun-agent-runtime --lib user_questions (6/6)
• cargo test -p openbitfun-core --lib session_activity_backfill (5/5)
• cargo test -p openbitfun-product-domains --lib remote_surface (19/19)
• cargo test -p openbitfun-cli --lib peer_host::commands::tests (2/2)
• cargo test -p openbitfun-cli --lib peer_host::commands::session::tests (9/9)

Host limitation:

• Focused openbitfun-desktop test binaries compile and link, but this Windows host exits before assertions with STATUS_ENTRYPOINT_NOT_FOUND (0xc0000139) for both the UI metadata field-mask test and remote_workspace_policy. This is an environment/runtime-loader failure, not a test assertion failure; CI is expected to exercise them in a clean environment.

Reviewer Notes

• Peer Device Mode was exercised through the generated operation registry plus CLI peer closure/session tests.
• Remote workspace, remote control, and detached dispatch were not exercised end to end.
• Browser/native visual acceptance was not performed. No mock or browser automation was used for visual validation.
• The first 50% worker run of the 39 Web test files hit two 10-second setup-hook timeouts while importing i18n/jsdom; both isolated files passed 11/11, and the full suite then passed 663/663 at 25% workers.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.