Goal

Implement graduated attention levels (🔴 urgent / 🟡 warning / 🟢 info) replacing the current binary SessionNeedsAttention() logic.

Scope

• In: New AttentionLevel type with Urgent/Warning/Info/None values, updated SessionAttentionLevel() function, updated filter/count helpers, updated mission dashboard and task detail attention displays
• Out: User-configurable thresholds (future work), finer-grained status from upstream (Investigate finer-grained session status: running vs awaiting-user #121)

Acceptance Criteria

• AttentionLevel enum: Urgent (failed, needs-input), Warning (running but idle >2h, queued >30min), Info (completed with notes), None
• New SessionAttentionLevel(s Session) AttentionLevel function in internal/data/session.go
• Existing SessionNeedsAttention() preserved as convenience wrapper (level == Urgent)
• Filter tab and header badge count updated to use graduated levels
• Mission dashboard shows graduated colors/icons
• Task detail attention banner shows level-appropriate styling
• Unit tests for all attention level derivations
• Extensible design so Investigate finer-grained session status: running vs awaiting-user #121 awaiting-user status slots in as Urgent when available

Dependencies

• Parent: UI Rework: Make agent-viz more helpful and better looking #192
• Related: Revisit: what should "needs attention" mean? #187, Investigate finer-grained session status: running vs awaiting-user #121

Validation

Run go test ./internal/data/... ./internal/tui/... — all pass. Visual inspection of attention indicators across views.