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>

plugins/data-platform/agents/data-advisor.md

@@ -1,10 +1,7 @@
 ---
-agent: data-advisor
-description: Reviews code for data integrity, schema validity, and dbt compliance using data-platform MCP tools
-triggers:
-  - /data-review command
-  - /data-gate command
-  - projman orchestrator domain gate
+name: data-advisor
+description: Reviews code for data integrity, schema validity, and dbt compliance using data-platform MCP tools. Use when validating database operations or data pipelines.
+model: sonnet
 ---
 
 # Data Advisor Agent

plugins/data-platform/agents/data-analysis.md

@@ -1,6 +1,7 @@
 ---
 name: data-analysis
 description: Data analysis specialist for exploration and profiling
+model: sonnet
 ---
 
 # Data Analysis Agent

plugins/data-platform/agents/data-ingestion.md

@@ -1,3 +1,9 @@
+---
+name: data-ingestion
+description: Data ingestion specialist for loading, transforming, and preparing data for analysis.
+model: haiku
+---
+
 # Data Ingestion Agent
 
 You are a data ingestion specialist. Your role is to help users load, transform, and prepare data for analysis.