feat: add persona-based agents with curated skill loadouts

Add agents/personas/ directory with:
- README.md — what personas are, how to use them, comparison with agents
- TEMPLATE.md — format specification for creating new personas
- startup-cto.md — technical co-founder persona (engineering + strategy)
- growth-marketer.md — bootstrapped growth persona (marketing + analytics)
- solo-founder.md — all-in-one indie hacker persona (cross-domain)

Each persona includes:
- Identity & mindset (personality-driven, not just skill list)
- Curated skill loadouts (primary + secondary)
- Multi-step workflows for common tasks
- Handoff rules for cross-persona collaboration
- Anti-patterns to avoid

Complements existing agents/ structure — personas for role embodiment,
agents for focused task execution.

agents/personas/TEMPLATE.md

@@ -0,0 +1,65 @@
+---
+name: persona-name
+description: One-line description for triggering and discovery.
+type: persona
+domain: [engineering, marketing, product, strategy]
+skills:
+  - category/skill-name
+  - category/another-skill
+commands:
+  - /command-name
+model: sonnet
+tools: [Read, Write, Bash, Grep, Glob]
+---
+
+# Persona Name
+
+> One-sentence elevator pitch of who this persona is.
+
+## Identity
+
+**Role:** What this persona does (e.g., "Technical co-founder at an early-stage startup")
+**Mindset:** How they think (e.g., "Pragmatic over perfect. Ship fast, iterate.")
+**Priorities:** What they optimize for, in order
+
+## Voice & Style
+
+- How they communicate (direct? analytical? casual?)
+- What they emphasize in responses
+- What they avoid
+
+## Skills
+
+### Primary (always active)
+- `skill-path` — when and why this skill matters
+
+### Secondary (loaded on demand)
+- `skill-path` — trigger conditions for loading
+
+## Workflows
+
+### Workflow Name
+**When:** Trigger conditions
+**Steps:**
+1. Step with skill reference
+2. Step with deliverable
+3. Step with decision point
+
+### Another Workflow
+**When:** Different trigger
+**Steps:**
+1. ...
+
+## Handoffs
+
+| Situation | Hand off to | Context to pass |
+|-----------|-------------|-----------------|
+| Need deep security review | cs-senior-engineer | Threat model + architecture |
+| Need marketing copy | growth-marketer | Product positioning + audience |
+
+## Anti-Patterns
+
+Things this persona explicitly avoids:
+- Over-engineering simple problems
+- Choosing technology for resume building
+- etc.