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/README.md

@@ -25,7 +25,7 @@ Developer guides for contributing to Mosaic Stack.
   - [Branching Strategy](2-development/1-workflow/1-branching.md)
   - [Testing Requirements](2-development/1-workflow/2-testing.md)
 - **[Database](2-development/2-database/)**
-  - Schema, migrations, and Prisma guides *(to be added)*
+  - Schema, migrations, and Prisma guides _(to be added)_
 - **[Type Sharing](2-development/3-type-sharing/)**
   - [Type Sharing Strategy](2-development/3-type-sharing/1-strategy.md)
 
@@ -33,8 +33,8 @@ Developer guides for contributing to Mosaic Stack.
 
 Technical architecture and design decisions.
 
-- **[Overview](3-architecture/1-overview/)** — System design *(to be added)*
-- **[Authentication](3-architecture/2-authentication/)** — BetterAuth and OIDC *(to be added)*
+- **[Overview](3-architecture/1-overview/)** — System design _(to be added)_
+- **[Authentication](3-architecture/2-authentication/)** — BetterAuth and OIDC _(to be added)_
 - **[Design Principles](3-architecture/3-design-principles/)**
   - [PDA-Friendly Patterns](3-architecture/3-design-principles/1-pda-friendly.md)
 
@@ -59,21 +59,25 @@ Development notes and implementation details for specific issues:
 ## 🔍 Quick Links
 
 ### For New Users
+
 1. [Quick Start](1-getting-started/1-quick-start/1-overview.md)
 2. [Local Setup](1-getting-started/2-installation/2-local-setup.md)
 3. [Environment Configuration](1-getting-started/3-configuration/1-environment.md)
 
 ### For Developers
+
 1. [Branching Strategy](2-development/1-workflow/1-branching.md)
 2. [Testing Requirements](2-development/1-workflow/2-testing.md)
 3. [Type Sharing](2-development/3-type-sharing/1-strategy.md)
 
 ### For Architects
+
 1. [PDA-Friendly Design](3-architecture/3-design-principles/1-pda-friendly.md)
-2. [Authentication Flow](3-architecture/2-authentication/) *(to be added)*
-3. [System Overview](3-architecture/1-overview/) *(to be added)*
+2. [Authentication Flow](3-architecture/2-authentication/) _(to be added)_
+3. [System Overview](3-architecture/1-overview/) _(to be added)_
 
 ### For API Consumers
+
 1. [API Conventions](4-api/1-conventions/1-endpoints.md)
 2. [Authentication Endpoints](4-api/2-authentication/1-endpoints.md)
 
@@ -112,6 +116,7 @@ Numbers maintain order in file systems and Bookstack.
 ### Code Examples
 
 Always include:
+
 - Language identifier for syntax highlighting
 - Complete, runnable examples
 - Expected output when relevant
@@ -143,14 +148,15 @@ Always include:
 
 ## 📊 Documentation Status
 
-| Book | Completion |
-|------|------------|
+| Book            | Completion  |
+| --------------- | ----------- |
 | Getting Started | 🟢 Complete |
-| Development | 🟡 Partial |
-| Architecture | 🟡 Partial |
-| API Reference | 🟡 Partial |
+| Development     | 🟡 Partial  |
+| Architecture    | 🟡 Partial  |
+| API Reference   | 🟡 Partial  |
 
 **Legend:**
+
 - 🟢 Complete
 - 🟡 Partial
 - 🔵 Planned