feat(backends): multi-backend intelligence layer — LLM + Agent backends, persona-loading agents, honest CLI commands

Add IntelligenceBackend abstraction with two categories:
- LLMBackend (OllamaLocal, OllamaCloud): CI runs tool loop, provides tools, constructs prompts
- AgentBackend (Opencode): agent runs own tool loop, CI serializes request

Refactor all 18 agents from hardcoded stubs to persona loaders that delegate
to the active backend or fail honestly when no backend is available.

Refactor OrchestratorAgent.executeStage() from monolithic switch to agent
delegation via STAGE_AGENT_MAP for intelligent stages (research, plan, execute,
verify), with mechanical stages (specify, clarify, complete) staying inline.

Wire CLI commands with --backend flag and auto-detection (opencode →
ollama-local → ollama-cloud). Harden rollback/ship with real git operations.
No command returns fake success.

src/agents/code-reviewer.ts

@@ -3,17 +3,26 @@ import { BaseAgent, AgentContext, AgentResult } from "./base.js";
 export class CodeReviewerAgent extends BaseAgent {
   readonly name = "code-reviewer";
   readonly description = "Multi-persona code review. Auto-applies P0 fixes. Flags P1+ for post-hoc review.";
+  readonly workflow = "review";
 
   async execute(context: AgentContext): Promise<AgentResult> {
-    this.log("Running code review...");
     const start = Date.now();
+    this.log("Running code review...");
+    if (context.backend) {
+      const result = await this.executeViaBackend(
+        context,
+        `Perform multi-persona code review for phase ${context.phase}. Specification: ${context.specification}`
+      );
+      return { ...result, duration_ms: Date.now() - start };
+    }
     return {
-      success: true,
-      output: "Code review complete — P0 fixes applied, P1+ flagged for review",
-      artifacts_created: ["CODE-REVIEW.md"],
+      success: false,
+      output: "Code review requires an intelligence backend. Configure one with: ci init --backend",
+      artifacts_created: [],
       decisions: 0,
       escalations: 0,
       duration_ms: Date.now() - start,
+      error: "No intelligence backend available",
     };
   }
 }