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/types/pipeline.ts

@@ -6,6 +6,7 @@ export type PipelineStage =
   | "research"
   | "plan"
   | "execute"
+  | "test"
   | "verify"
   | "complete";
 
@@ -19,6 +20,7 @@ export interface PipelineState {
   research_completed: boolean;
   plan_completed: boolean;
   execute_completed: boolean;
+  test_completed: boolean;
   verify_completed: boolean;
   errors: PipelineError[];
   started_at: string;
@@ -61,6 +63,7 @@ export const STAGE_ORDER: PipelineStage[] = [
   "research",
   "plan",
   "execute",
+  "test",
   "verify",
   "complete",
 ];
@@ -84,6 +87,7 @@ export function createInitialPipelineState(
     research_completed: false,
     plan_completed: false,
     execute_completed: false,
+    test_completed: false,
     verify_completed: false,
     errors: [],
     started_at: new Date().toISOString(),