feat(agents): add model selection and standardize frontmatter

Add per-agent model selection using Claude Code's now-supported `model`
frontmatter field, and standardize all agent frontmatter across the
marketplace.

Changes:
- Add `model` field to all 25 agents (18 sonnet, 7 haiku)
- Fix viz-platform/data-platform agents using `agent:` instead of `name:`
- Remove non-standard `triggers:` field from domain agents
- Add missing frontmatter to 13 agents
- Document model selection in CLAUDE.md and CONFIGURATION.md
- Fix undocumented commands in README.md

Model assignments based on reasoning depth, tool complexity, and latency:
- sonnet: Planner, Orchestrator, Executor, Coordinator, Security Reviewers
- haiku: Maintainability Auditor, Test Validator, Git Assistant, etc.

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

docs/CONFIGURATION.md

@@ -496,6 +496,63 @@ Not all plugins have MCP servers. The install script handles this automatically:
 
 ---
 
+## Agent Model Selection
+
+Marketplace agents specify their preferred model using Claude Code's `model` frontmatter field. This allows cost/performance optimization per agent.
+
+### Supported Values
+
+| Value | Description |
+|-------|-------------|
+| `sonnet` | Default. Balanced performance and cost. |
+| `opus` | Higher reasoning depth. Use for complex analysis. |
+| `haiku` | Faster, lower cost. Use for mechanical tasks. |
+| `inherit` | Use session's current model setting. |
+
+### How It Works
+
+Each agent in `plugins/{plugin}/agents/{agent}.md` has frontmatter like:
+
+```yaml
+---
+name: planner
+description: Sprint planning agent - thoughtful architecture analysis
+model: sonnet
+---
+```
+
+Claude Code reads this field when invoking the agent as a subagent.
+
+### Model Assignments
+
+Agents are assigned models based on their task complexity:
+
+| Model | Agents | Rationale |
+|-------|--------|-----------|
+| **sonnet** | Planner, Orchestrator, Executor, Code Reviewer, Coordinator, Security Reviewers, Performance Analyst, Data Advisor, Data Analysis, Design Reviewer, Layout Builder, Full Validation, Doc Analyzer, Clarity Coach, Maintainer, CMDB Assistant, Refactor Advisor | Standard reasoning, tool orchestration, code generation |
+| **haiku** | Maintainability Auditor, Test Validator, Component Check, Theme Setup, Agent Check, Data Ingestion, Git Assistant | Pattern matching, quick validation, mechanical tasks |
+
+### Overriding Model Selection
+
+**Per-agent override:** Edit the `model:` field in the agent file:
+
+```bash
+# Change executor to use opus for heavy implementation work
+nano plugins/projman/agents/executor.md
+# Change model: sonnet to model: opus
+```
+
+**Session-level:** Users on Opus subscription can change the agent's model to `inherit` to use whatever model the session is using.
+
+### Best Practices
+
+1. **Default to sonnet** - Good balance for most tasks
+2. **Use haiku for speed-sensitive agents** - Sub-agents dispatched in parallel, read-only tasks
+3. **Reserve opus for heavy analysis** - Only when sonnet's reasoning isn't sufficient
+4. **Use inherit sparingly** - Only when you want session-level control
+
+---
+
 ## Automatic Validation Features
 
 ### API Validation