Tasks: Workspace visual refinement

Setup

• T001 Research references and record bounded acceptance in specs/048-workspace-refinement/spec.md and research.md.

US1 — Calm workspace scan

• T002 [US1] Add red generated/explicit/timed headline regressions in crates/signaltty-gui/src/sidebar.rs.
• T003 [US1] Implement provenance-aware headline hiding and decorative branch/directory image in crates/signaltty-gui/src/sidebar.rs.
• T004 [US1] Unify row/search/footer geometry and simplify selected surface in crates/signaltty-gui/data/style.css.

US2 — Native appearance and sizes

• T005 [US2] Extend existing display regression for metadata and refresh cases in crates/signaltty-gui/src/sidebar.rs; inspect light/dark/narrow/large/high-contrast native renders.

Delivery

• T006 Run full verification and independent diff/visual review; document evidence in specs/048-workspace-refinement/verification.md and docs/06-gui-toolkit.md.
• T007 Commit and open linked PR with sources and proof.

Dependencies: T001 → T002 → T003 → T004 → T005 → T006 → T007. Independent review can run alongside full verification after implementation. MVP is US1; US2 is required acceptance before submission.