refactor(cli): split console state contexts

[codeaholicguy]

Summary

• split agent and channel console state into focused contexts with stable provider values
• move HeaderBar and mixed consumers to the narrow hooks they require while retaining the combined hook for compatibility
• preserve input-focus polling pauses and stable refresh actions
• add an Ink render-count regression proving channel-only updates do not rerender agent-only consumers

Validation

• npm run test --workspace packages/cli -- src/__tests__/tui/console — 21 files, 126 tests passed
• npm run test --workspace packages/cli — 80 files, 960 tests passed
• npm run lint --workspace packages/cli — exit 0; 5 pre-existing warnings, 0 errors
• npm run build --workspace packages/cli — exit 0
• regression mutation check — failed 2 → 3 when the channel dependency was deliberately reintroduced, then passed after restoration

Risk

Low. Provider wiring and consumer subscriptions changed; polling hooks and console behavior remain unchanged.