feat(P01): add ideation engine + ciagent ideate command — IDEATE-01,02,03,17 + MULTI-01

---ci---
phase: 1
milestone: v0.10
status: execute
decisions:
  - id: D-080
    decision: Three-tier ideation (mechanical, backend-enriched, cross-project)
    rationale: Mechanical tier always produces output without backend
    confidence: 0.92
  - id: D-089
    decision: No separate codebase map command
    rationale: Git-native + .ciagent/ covers mapping; avoids tree-sitter dep
    confidence: 0.88
requirements:
  covered:
    - IDEATE-01
    - IDEATE-02
    - IDEATE-03
    - IDEATE-17
    - MULTI-01
---/ci---

Add IdeationEngine core module with 15 signal collectors:
- Uncovered/partial requirements from REQUIREMENTS.md
- Coverage gaps (documented but unimplemented agents)
- Repeated lessons from git history
- Low-confidence decisions from ---ci--- blocks
- Escalation patterns from git history
- Compound solution patterns
- Architecture drift (ARCHITECTURE.md vs src/)
- Verification inversion (missing test files)
- Improvement patterns (cross-referencing lessons + requirements)
- Spec ambiguity (should/could/might patterns)
- Spec missing (common requirement categories)
- Cascade impact (--affected from git diff)
- External signals (npm audit, dependency staleness)
- Cross-project lesson mining

Add ciagent ideate CLI command with flags:
--category, --affected, --spec, --external, --cross-project, --output

Add active_projects to CIAgentConfig (backwards compatible with active_project).
Add IDEATE pipeline stage between RESEARCH and PLAN.
Update IdeationAgent to delegate to IdeationEngine.

533 tests passing.

src/agents/ideation-agent.test.ts

@@ -4,74 +4,24 @@ import * as os from "node:os";
 import { IdeationAgent } from "../agents/ideation-agent.js";
 
 describe("IdeationAgent", () => {
-  let tempDir: string;
-
-  beforeEach(() => {
-    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "ciagent-ideation-test-"));
-  });
-
-  afterEach(() => {
-    fs.rmSync(tempDir, { recursive: true, force: true });
-  });
-
-  it("generates ideas from uncovered requirements", () => {
-    const ciagentDir = path.join(tempDir, ".ciagent");
-    fs.mkdirSync(ciagentDir, { recursive: true });
-    fs.writeFileSync(
-      path.join(ciagentDir, "REQUIREMENTS.md"),
-      "REQ-1: First requirement\nREQ-2: Second requirement"
-    );
-
-    const agent = new IdeationAgent();
-    const ideas = agent.mechanicalIdeate(tempDir);
-
-    const reqIdeas = ideas.filter((i) => i.source === "uncovered_requirement");
-    expect(reqIdeas.length).toBeGreaterThanOrEqual(2);
-    expect(reqIdeas.some((i) => i.relatedReq === "REQ-1")).toBe(true);
-  });
-
-  it("identifies coverage gaps from PROJECT.md", () => {
-    const ciagentDir = path.join(tempDir, ".ciagent");
-    fs.mkdirSync(ciagentDir, { recursive: true });
-    fs.writeFileSync(
-      path.join(ciagentDir, "PROJECT.md"),
-      "We use agent: magic-agent and agent: super-agent for tasks."
-    );
-
-    const srcDir = path.join(tempDir, "src", "agents");
-    fs.mkdirSync(srcDir, { recursive: true });
-    fs.writeFileSync(path.join(srcDir, "base.ts"), "");
-    fs.writeFileSync(path.join(srcDir, "index.ts"), "");
-
-    const agent = new IdeationAgent();
-    const gaps = agent.identifyCoverageGaps(tempDir);
-
-    expect(gaps).toContain("magic-agent");
-    expect(gaps).toContain("super-agent");
-  });
-
-  it("finds repeated patterns from lessons list", () => {
-    const agent = new IdeationAgent();
-    const lessons = [
-      { topic: "testing", detail: "testing: tests are flaky" },
-      { topic: "testing", detail: "testing: more test failures" },
-      { topic: "build", detail: "build: CI broken" },
-    ];
-
-    const repeated = agent.findRepeatedPatterns(lessons);
-    expect(repeated).toContain("testing");
-    expect(repeated).not.toContain("build");
-  });
-
-  it("returns empty ideas when no project files exist", () => {
-    const agent = new IdeationAgent();
-    const ideas = agent.mechanicalIdeate(tempDir);
-
-    expect(ideas).toEqual(expect.arrayContaining([]));
-  });
-
   it("agent name is ideation-agent", () => {
     const agent = new IdeationAgent();
     expect(agent.name).toBe("ideation-agent");
   });
+
+  it("workflow is research", () => {
+    const agent = new IdeationAgent();
+    expect(agent.workflow).toBe("research");
+  });
+
+  it("delegates mechanicalIdeate to IdeationEngine", () => {
+    const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "ciagent-agent-test-"));
+    try {
+      const agent = new IdeationAgent();
+      const ideas = agent.mechanicalIdeate(tempDir);
+      expect(Array.isArray(ideas)).toBe(true);
+    } finally {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    }
+  });
 });