feat(agents): update agent definitions with CEP content

[marcusrbrown]

This commit removes placeholder agent stubs into fully-featured agent specifications with detailed instructions, workflows, and usage examples.

Changes:

• framework-docs-researcher: Add comprehensive documentation gathering workflow, MANDATORY deprecation checks for external APIs, Context7 integration guidance,
  and structured output format with 7-section reporting template
• architecture-strategist: Expand with systematic architecture analysis approach, SOLID principles verification, coupling metrics, API contract stability checks,
  and structured 5-section output format
• code-simplicity-reviewer: Detail YAGNI principles, 6-step review process for ruthless simplification, specific guidance for challenging abstractions and
  removing redundancy, with markdown template for simplification analysis
• pattern-recognition-specialist: Add comprehensive pattern detection workflow, anti-pattern identification (TODO/FIXME/HACK scanning), naming convention
  analysis, code duplication detection with tool recommendations (jscpd)
• performance-oracle: Expand with 6-category analysis framework (algorithmic complexity, database, memory, caching, network, frontend), specific performance benchmarks, and structured output format with scalability assessment

All agents now include:

• Rich contextual descriptions with usage examples in YAML frontmatter
• "model: inherit" configuration for consistent model usage
• Detailed workflow processes and quality standards
• Structured output formats for consistent reporting
• Language-specific considerations (Rails, JavaScript, etc.)