Add Abacus AI TUI agent integration with sleeping-session resume support

## Summary
Add first-class Abacus AI support to Orca's TUI agent pipeline, including launch/detection wiring, status hook normalization, icon/catalog entries, and sleeping-session resume support.

## Scope
- Add `abacusai` to shared `TuiAgent` unions and selection/search/token matching
- Add launch config/defaults and startup plan coverage
- Add catalog entry and bundled icon wiring
- Add hook source + listener normalization and route handling for `/hook/abacusai`
- Add resume metadata extraction + argv generation (`--resume `)
- Add test coverage for resume and startup plan behavior

## Acceptance Criteria
- Abacus AI appears in agent picker/catalog with icon
- New Abacus AI sessions launch correctly via Orca
- Sleeping Abacus AI sessions can be resumed from stored provider session metadata
- Hook payloads from `/hook/abacusai` are accepted/normalized without type errors
- Targeted tests pass for:
- `src/shared/agent-session-resume.test.ts`
- `src/shared/tui-agent-startup.test.ts`
- `src/shared/agent-hook-listener.test.ts`

## Notes
Current work branch: `Add-abacusai-agent`