feat(FN-1443): create dedicated soul.md files for all New Agent presets

- Add soul.md files for 20 agent presets (backend-engineer, ceo, cfo, ci-engineer, cmo, cto, data-engineer, designer, devops-engineer, engineer, frontend-engineer, fullstack-engineer, marketing-manager, ml-engineer, product-manager, qa-engineer, reviewer, security-engineer, technical-writer, triage)
- Create agent-presets/index.ts module exporting all preset definitions
- Refactor NewAgentDialog to use centralized agent-presets module
- Add comprehensive tests for agent presets validation
- Update docs/agents.md with agent preset documentation

docs/agents.md

@@ -40,6 +40,86 @@ Agents can be configured with:
 
 Heartbeat values are validated and minimum-clamped.
 
+## New Agent Presets (Dashboard UI)
+
+The New Agent dialog in the dashboard provides quick-start presets for common agent roles. Each preset includes:
+
+- **Name and icon** — Display identification
+- **Professional title** — Descriptive role title
+- **Soul** — Personality and operating principles defining how the agent thinks and communicates
+- **Instructions** — Actionable behavioral guidelines
+
+### Preset Library Location
+
+Preset definitions live in `packages/dashboard/app/components/agent-presets/`:
+
+```
+agent-presets/
+├── index.ts              # Exports AGENT_PRESETS and helper functions
+├── ceo/soul.md          # Chief Executive Officer soul
+├── cto/soul.md          # Chief Technology Officer soul
+├── cmo/soul.md          # Chief Marketing Officer soul
+├── cfo/soul.md          # Chief Financial Officer soul
+├── engineer/soul.md     # Software Engineer soul
+├── backend-engineer/soul.md
+├── frontend-engineer/soul.md
+├── fullstack-engineer/soul.md
+├── qa-engineer/soul.md
+├── devops-engineer/soul.md
+├── ci-engineer/soul.md
+├── security-engineer/soul.md
+├── data-engineer/soul.md
+├── ml-engineer/soul.md
+├── product-manager/soul.md
+├── designer/soul.md
+├── marketing-manager/soul.md
+├── technical-writer/soul.md
+├── triage/soul.md
+└── reviewer/soul.md
+```
+
+### Soul File Format
+
+Each `soul.md` file is a Markdown document containing:
+
+```markdown
+# Soul: [Role Name]
+
+[First-person identity statement]
+
+## Operating Principles
+
+[Bullet points describing key behaviors]
+
+## Communication Style
+
+[How the agent communicates]
+```
+
+Soul content should be:
+
+- **First-person** — Written from the agent's perspective ("I am...")
+- **Role-specific** — Defines the unique character of this role
+- **Actionable** — Describes concrete behaviors, not abstract qualities
+- **Paperclip-inspired** — Clear ownership, decision discipline, communication standards
+
+### Adding or Modifying Presets
+
+1. Create or edit the `soul.md` file in the appropriate directory
+2. Update `index.ts` if adding a new preset (export the imported soul and add to `AGENT_PRESETS` array)
+3. Run tests to verify: `pnpm --filter @fusion/dashboard exec vitest run app/components/__tests__/agent-presets.test.ts`
+
+### Preset vs Engine Templates
+
+**Dashboard presets** are a UI-only concept that populates the New Agent dialog fields (name, icon, role, soul, instructionsText). They don't map to engine types.
+
+**Engine role prompts** (in `agentPrompts` settings) define the actual agent behavior when executing tasks. These are separate from dashboard presets and live in project settings.
+
+This separation means:
+- Presets provide starting point personality and instructions for new agents
+- Engine templates control actual task execution behavior
+- An agent created from a preset can have its engine role prompt customized independently
+
 ## Configurable Agent Prompts (`agentPrompts`)
 
 `agentPrompts` project setting supports: