refactor(rebrand): rename & rebrand CI → CIAgent across all source and test files

- Type renames: CIConfig → CIAgentConfig, DEFAULT_CI_CONFIG → DEFAULT_CIAGENT_CONFIG
- Type renames: CiMetadata → CIAgentMetadata, ParsedCiCommit → ParsedCIAgentCommit
- Function renames: initCI → initCIAgent, isCIInitialized → isCIAgentInitialized
- Function renames: extractCiBlock → extractCIAgentBlock, parseCiBlock → parseCIAgentBlock
- Class renames: CiFiles → CIAgentFiles
- Import paths: ci-files.js → ciagent-files.js
- Directory paths: .ci/ → .ciagent/ across all source and test files
- Check names: ".ci directory exists" → ".ciagent directory exists"
- Check names: "CI config valid" → "CIAgent config valid"
- Temp dir names: ci-*-test- → ciagent-*-test-
- CLI examples: "ci init" → "ciagent init"
- Fix deepMerge infinite recursion bug in config.ts
- ---ci---/---/ci--- block markers preserved unchanged
- All 31 test suites, 370 tests passing

---ci---
phase: 1
milestone: v0.5
plan: 07
task: 07-01-01
status: execute
---/ci---

src/agents/index.ts

@@ -17,6 +17,7 @@ export { ProjectResearcherAgent } from "./project-researcher.js";
 export { ResearchSynthesizerAgent } from "./research-synthesizer.js";
 export { SolutionWriterAgent } from "./solution-writer.js";
 export { PhaseResearcherAgent } from "./phase-researcher.js";
+export { TesterAgent } from "./tester.js";
 
 import { AgentName } from "../types/config.js";
 import { BaseAgent as BaseAgentType } from "./base.js";
@@ -38,6 +39,7 @@ import { ProjectResearcherAgent } from "./project-researcher.js";
 import { ResearchSynthesizerAgent } from "./research-synthesizer.js";
 import { SolutionWriterAgent } from "./solution-writer.js";
 import { PhaseResearcherAgent } from "./phase-researcher.js";
+import { TesterAgent } from "./tester.js";
 
 const agentRegistry: Record<AgentName, () => BaseAgentType> = {
   orchestrator: () => new OrchestratorAgent(),
@@ -58,6 +60,7 @@ const agentRegistry: Record<AgentName, () => BaseAgentType> = {
   "project-researcher": () => new ProjectResearcherAgent(),
   "research-synthesizer": () => new ResearchSynthesizerAgent(),
   "solution-writer": () => new SolutionWriterAgent(),
+  tester: () => new TesterAgent(),
 };
 
 export function getAgent(name: AgentName): BaseAgentType {