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/types.ts

@@ -1255,37 +1255,6 @@ export interface ImageDetectedEvent {
   size: number;
 }
 
-// ========== Execution Bridge Re-exports ==========
+// ========== Plan Orchestrator Re-exports ==========
 
-export type {
-  ExecutionStatus,
-  ExecutionProgress,
-  TaskAssignment as ExecutionTaskAssignment,
-  PlanItem,
-  ExecutionHistoryEntry,
-} from './execution-bridge.js';
-
-export type {
-  ModelTier,
-  AgentType,
-  ExecutionMode,
-  ModelConfig,
-  ModelSelection,
-  ExecutionModeSelection,
-  TaskCharacteristics,
-} from './model-selector.js';
-
-export type {
-  GroupTaskStatus,
-  ExecutionGroupStatus,
-  GroupTask,
-  ExecutionGroup,
-  ExecutionSchedule,
-} from './group-scheduler.js';
-
-export type {
-  ContextRefreshMethod,
-  ContextRefreshStatus,
-  ContextRefreshRequest,
-  ContextRefreshResult,
-} from './context-manager.js';
+export type { PlanItem } from './plan-orchestrator.js';