feat(#93): implement agent spawn via federation

Implements FED-010: Agent Spawn via Federation feature that enables
spawning and managing Claude agents on remote federated Mosaic Stack
instances via COMMAND message type.

Features:
- Federation agent command types (spawn, status, kill)
- FederationAgentService for handling agent operations
- Integration with orchestrator's agent spawner/lifecycle services
- API endpoints for spawning, querying status, and killing agents
- Full command routing through federation COMMAND infrastructure
- Comprehensive test coverage (12/12 tests passing)

Architecture:
- Hub → Spoke: Spawn agents on remote instances
- Command flow: FederationController → FederationAgentService →
  CommandService → Remote Orchestrator
- Response handling: Remote orchestrator returns agent status/results
- Security: Connection validation, signature verification

Files created:
- apps/api/src/federation/types/federation-agent.types.ts
- apps/api/src/federation/federation-agent.service.ts
- apps/api/src/federation/federation-agent.service.spec.ts

Files modified:
- apps/api/src/federation/command.service.ts (agent command routing)
- apps/api/src/federation/federation.controller.ts (agent endpoints)
- apps/api/src/federation/federation.module.ts (service registration)
- apps/orchestrator/src/api/agents/agents.controller.ts (status endpoint)
- apps/orchestrator/src/api/agents/agents.module.ts (lifecycle integration)

Testing:
- 12/12 tests passing for FederationAgentService
- All command service tests passing
- TypeScript compilation successful
- Linting passed

Refs #93

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/2-development/1-workflow/1-branching.md

@@ -7,11 +7,13 @@ Git workflow and branching conventions for Mosaic Stack.
 ### Main Branches
 
 **`main`** — Production-ready code only
+
 - Never commit directly
 - Only merge from `develop` via release
 - Tagged with version numbers
 
 **`develop`** — Active development (default branch)
+
 - All features merge here first
 - Must always build and pass tests
 - Protected branch
@@ -19,6 +21,7 @@ Git workflow and branching conventions for Mosaic Stack.
 ### Supporting Branches
 
 **`feature/*`** — New features
+
 ```bash
 # From: develop
 # Merge to: develop
@@ -30,6 +33,7 @@ git checkout -b feature/6-frontend-auth
 ```
 
 **`fix/*`** — Bug fixes
+
 ```bash
 # From: develop (or main for hotfixes)
 # Merge to: develop (or both main and develop)
@@ -40,6 +44,7 @@ git checkout -b fix/12-session-timeout
 ```
 
 **`refactor/*`** — Code improvements
+
 ```bash
 # From: develop
 # Merge to: develop
@@ -49,6 +54,7 @@ git checkout -b refactor/auth-service-cleanup
 ```
 
 **`docs/*`** — Documentation updates
+
 ```bash
 # From: develop
 # Merge to: develop