feat(agentic): implement §9 Services (FleetService + CreditService + SessionService) (#849)
Additive-only — no existing files modified.
- FleetService: wraps fleet actions+models, register/heartbeat/dispatch
(direct or queued), node health snapshots, typed fleet stats
- CreditService: workspace-level balance/refund/deduct/ledger over
credit_entries, returns typed CreditTransaction DTOs
- SessionService: RFC-§7 lifecycle session creation + guarded state
transitions + SSE-style emission via Laravel events
DTOs: FleetStats, CreditTransaction (readonly).
Pest Feature tests _Good/_Bad/_Ugly per AX-10. pest skipped (vendor missing).
Co-authored-by: Codex <noreply@openai.com>
Closes tasks.lthn.sh/view.php?id=849
470ce0de99