Wire swarm into `il start` entry point

[acreeger]

Summary

Connect epic detection, Beads integration, and the supervisor loop into the il start command to deliver the end-to-end swarm experience.

Context

Part of the Autonomous Swarm Mode epic (#557). This is the final integration issue that wires all the pieces together into a working il start <epic> → swarm flow.

Scope

Entry Point Flow

In StartCommand.execute(), after input parsing and validation:

1. Fetch issue details (existing)
2. Check for iloom-epic label (from #559)
3. If epic detected:
   a. Show confirmation prompt (from #559)
   b. Create epic loom with integration branch (from #559)
   c. Initialize BeadsManager (from #558)
   d. Sync epic children + deps to Beads (from #558)
   e. Create SwarmSupervisor (from #562)
   f. Launch supervisor as foreground process
   g. On supervisor completion: report results, exit
4. If not epic: proceed with normal il start flow (unchanged)

CLI Wiring in cli.ts

• Add --swarm option to il start
• Add --max-agents <n> option to il start
• Pass these through to StartCommand

Dependency Injection

Wire up SwarmSupervisor with all its dependencies:

• BeadsManager (from settings)
• LoomManager (existing)
• IssueTracker (existing)
• SwarmSettings (from SettingsManager)

Integration Testing

• Test: il start <epic> with mock epic → detects, confirms, creates loom, runs supervisor
• Test: il start <epic> --swarm → skips confirmation
• Test: il start <non-epic> → normal flow unaffected
• Test: il start <non-epic> --swarm → --swarm silently ignored
• Test: graceful shutdown with Ctrl+C

Documentation

• Update docs/iloom-commands.md with swarm mode documentation
• Add --swarm and --max-agents flags to il start documentation
• Document swarm settings section
• Add swarm mode overview to README.md

Acceptance Criteria

• il start <epic-number> detects epic, confirms, and runs swarm end-to-end
• il start <epic-number> --swarm bypasses confirmation
• il start <epic-number> --max-agents 5 overrides setting
• Normal il start (non-epic) is completely unaffected
• All dependencies correctly wired
• Integration tests pass
• Documentation updated

Scope Boundaries

• This is pure wiring/integration — no new core logic
• All pieces should be individually working from prior issues

Dependencies

• Epic detection and setup in il start #559 (Epic detection) — detection + confirmation + epic loom creation
• Swarm supervisor loop with sequential merge queue #562 (Supervisor loop) — the core orchestrator
• Supervisor resilience: failure handling, conflict resolution, and observability #563 (Resilience) — failure handling, conflict resolution, progress reporting