refactor: simplify ralph wizard from 9 agents to 2

Remove execution layer that never actually controlled execution:
- execution-bridge.ts (model param was ignored)
- group-scheduler.ts (task-tool mode never used)
- model-selector.ts (recommendations were display-only)
- context-manager.ts (never invoked)
- execution-limits.ts

Remove redundant agent prompts (overlapping outputs):
- requirements-analyst, architecture-planner, risk-analyst
- testing-specialist, verification (merged into planner.ts)
- execution-optimizer (output was ignored)
- final-review (scores were cosmetic)

Simplify plan-orchestrator.ts from 2400 LOC to 520 LOC:
- Before: 9 agents, 6 phases, ~40-60 minutes
- After: 2 agents (research + planner), ~18 minutes

Remove /api/execution/* endpoints and related server code.

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

src/prompts/planner.ts

@@ -0,0 +1,83 @@
+/**
+ * Planner Prompt - Single agent for TDD plan generation
+ *
+ * Combines what was previously 5 separate agents:
+ * - Requirements Analyst (redundant)
+ * - Architecture Planner (redundant)
+ * - Testing Specialist (kept - TDD focus)
+ * - Risk Analyst (redundant)
+ * - Verification Expert (kept - structure)
+ *
+ * Placeholders: {TASK}, {RESEARCH_CONTEXT}
+ */
+
+export const PLANNER_PROMPT = `You are a TDD Plan Generator. Create a complete implementation plan with test-first approach.
+
+## TASK DESCRIPTION
+{TASK}
+
+{RESEARCH_CONTEXT}
+
+## YOUR MISSION
+Generate a complete TDD implementation plan with:
+1. Tests BEFORE implementations (red-green-refactor)
+2. Review tasks AFTER implementations
+3. Clear priorities (P0=blocking, P1=required, P2=polish)
+4. Dependencies between tasks
+
+## TDD CYCLE
+For each feature:
+1. Write failing test first
+2. Implement to make test pass
+3. Review implementation
+
+## PRIORITY GUIDELINES
+- P0: Foundation, types, project setup, blocking dependencies
+- P1: Core features, main implementation, error handling
+- P2: Polish, optimization, documentation
+
+## OUTPUT FORMAT
+Return ONLY a JSON object:
+{
+  "items": [
+    {
+      "id": "P0-001",
+      "content": "Write failing test for user authentication endpoint",
+      "priority": "P0",
+      "tddPhase": "test",
+      "verificationCriteria": "Test file exists, test fails with 'not implemented'",
+      "testCommand": "npm test -- --grep='auth'",
+      "dependencies": []
+    },
+    {
+      "id": "P0-002",
+      "content": "Implement user authentication handler",
+      "priority": "P0",
+      "tddPhase": "impl",
+      "verificationCriteria": "npm test -- --grep='auth' passes",
+      "pairedWith": "P0-001",
+      "dependencies": ["P0-001"]
+    },
+    {
+      "id": "P0-003",
+      "content": "Review auth implementation for security",
+      "priority": "P0",
+      "tddPhase": "review",
+      "verificationCriteria": "No security issues, follows best practices",
+      "reviewChecklist": ["Input validation", "XSS prevention", "Error handling"],
+      "pairedWith": "P0-002",
+      "dependencies": ["P0-002"]
+    }
+  ],
+  "gaps": ["any missing requirements noted"],
+  "warnings": ["any concerns or risks identified"]
+}
+
+CRITICAL REQUIREMENTS:
+1. Every implementation MUST have a paired test task that comes BEFORE it
+2. Every implementation MUST have a review task that comes AFTER it
+3. Use sequential IDs: P0-001, P0-002, P1-001, etc.
+4. verificationCriteria must be SPECIFIC and observable
+5. Dependencies must form a valid DAG (no cycles)
+
+Generate 15-40 items covering the complete implementation.`;