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.ts

@@ -1,18 +1,9 @@
-import * as fs from "node:fs";
-import * as path from "node:path";
 import { BaseAgent, AgentContext, AgentResult } from "./base.js";
-
-interface Idea {
-  source: "uncovered_requirement" | "repeated_lesson" | "gap_in_coverage" | "improvement_pattern";
-  title: string;
-  rationale: string;
-  confidence: number;
-  relatedReq?: string;
-}
+import { IdeationEngine } from "../core/ideation.js";
 
 export class IdeationAgent extends BaseAgent {
   readonly name = "ideation-agent";
-  readonly description = "Generates improvement ideas. Output feeds directly into planning pipeline.";
+  readonly description = "Generates improvement ideas using git-native pattern mining, coverage gap analysis, and architectural drift detection. Output feeds directly into planning pipeline.";
   readonly workflow = "research";
 
   async execute(context: AgentContext): Promise<AgentResult> {
@@ -27,8 +18,9 @@ export class IdeationAgent extends BaseAgent {
       return { ...result, duration_ms: Date.now() - start };
     }
 
-    const ideas = this.mechanicalIdeate(context.project_path);
-    const output = this.formatIdeas(ideas);
+    const engine = new IdeationEngine(context.project_path);
+    const ideas = engine.runMechanical();
+    const output = engine.formatIdeas(ideas);
 
     return {
       success: true,
@@ -40,153 +32,8 @@ export class IdeationAgent extends BaseAgent {
     };
   }
 
-  mechanicalIdeate(projectPath: string): Idea[] {
-    const ideas: Idea[] = [];
-    const uncoveredReqs = this.readUncoveredRequirements(projectPath);
-    const lessons = this.readRecentLessons(projectPath);
-    const repeated = this.findRepeatedPatterns(lessons);
-    const coverageGaps = this.identifyCoverageGaps(projectPath);
-
-    for (const req of uncoveredReqs) {
-      ideas.push({
-        source: "uncovered_requirement",
-        title: `Address uncovered requirement: ${req}`,
-        rationale: `Requirement ${req} has no corresponding implementation task.`,
-        confidence: 0.8,
-        relatedReq: req,
-      });
-    }
-
-    for (const topic of repeated) {
-      ideas.push({
-        source: "repeated_lesson",
-        title: `Investigate repeated lesson: ${topic}`,
-        rationale: `Topic "${topic}" appears in multiple commit lessons, indicating a systemic issue.`,
-        confidence: 0.7,
-      });
-    }
-
-    for (const gap of coverageGaps) {
-      ideas.push({
-        source: "gap_in_coverage",
-        title: `Fill coverage gap: ${gap}`,
-        rationale: `Agent "${gap}" is claimed in PROJECT.md but not found in the agent registry.`,
-        confidence: 0.75,
-      });
-    }
-
-    this.generateIdeas(uncoveredReqs, repeated, ideas);
-
-    return ideas;
-  }
-
-  readUncoveredRequirements(projectPath: string): string[] {
-    const reqPath = path.join(projectPath, ".ciagent", "REQUIREMENTS.md");
-    if (!fs.existsSync(reqPath)) return [];
-
-    const content = fs.readFileSync(reqPath, "utf-8");
-    const reqIds: string[] = [];
-    const reqIdRegex = /REQ-(\d+)/g;
-    let match;
-    while ((match = reqIdRegex.exec(content)) !== null) {
-      reqIds.push(`REQ-${match[1]}`);
-    }
-
-    const planPath = path.join(projectPath, ".ciagent", "PLAN.md");
-    if (!fs.existsSync(planPath)) return reqIds;
-
-    const planContent = fs.readFileSync(planPath, "utf-8");
-    const coveredReqIds = new Set<string>();
-    const planRegex = /REQ-(\d+)/g;
-    let planMatch;
-    while ((planMatch = planRegex.exec(planContent)) !== null) {
-      coveredReqIds.add(`REQ-${planMatch[1]}`);
-    }
-
-    return reqIds.filter((id) => !coveredReqIds.has(id));
-  }
-
-  readRecentLessons(projectPath: string): Array<{ topic: string; detail: string }> {
-    const lessons: Array<{ topic: string; detail: string }> = [];
-    try {
-      const { execSync } = require("node:child_process");
-      const log = execSync('git log --grep="lessons:" --format="%B" -50', {
-        cwd: projectPath,
-        encoding: "utf-8",
-        timeout: 5000,
-      });
-      const lessonsRegex = /lessons:\s*\n((?:\s+-\s+.+\n?)+)/g;
-      let match;
-      while ((match = lessonsRegex.exec(log)) !== null) {
-        const items = match[1].split("\n").filter((l: string) => l.trim().startsWith("-"));
-        for (const item of items) {
-          const detail = item.replace(/^\s*-\s*/, "").trim();
-          const topic = detail.split(":")[0].trim().toLowerCase();
-          lessons.push({ topic, detail });
-        }
-      }
-    } catch {}
-
-    return lessons;
-  }
-
-  findRepeatedPatterns(lessons: Array<{ topic: string; detail: string }>): string[] {
-    const counts: Record<string, number> = {};
-    for (const lesson of lessons) {
-      counts[lesson.topic] = (counts[lesson.topic] || 0) + 1;
-    }
-    return Object.entries(counts)
-      .filter(([, count]) => count > 1)
-      .map(([topic]) => topic);
-  }
-
-  generateIdeas(uncoveredReqs: string[], repeated: string[], ideas: Idea[]): void {
-    const repeatedSet = new Set(repeated.map((r) => r.toLowerCase()));
-    for (const req of uncoveredReqs) {
-      for (const topic of repeated) {
-        if (req.toLowerCase().includes(topic) || topic.includes(req.toLowerCase())) {
-          ideas.push({
-            source: "improvement_pattern",
-            title: `Cross-reference: ${req} ↔ ${topic}`,
-            rationale: `Repeated lesson "${topic}" directly relates to uncovered requirement ${req}.`,
-            confidence: 0.85,
-            relatedReq: req,
-          });
-        }
-      }
-    }
-  }
-
-  identifyCoverageGaps(projectPath: string): string[] {
-    const projectMdPath = path.join(projectPath, ".ciagent", "PROJECT.md");
-    if (!fs.existsSync(projectMdPath)) return [];
-
-    const content = fs.readFileSync(projectMdPath, "utf-8");
-    const agentMentionRegex = /(?:agent|Agent):\s*(\S+)/g;
-    const mentionedAgents: string[] = [];
-    let match;
-    while ((match = agentMentionRegex.exec(content)) !== null) {
-      mentionedAgents.push(match[1]);
-    }
-
-    const agentsDir = path.join(projectPath, "src", "agents");
-    if (!fs.existsSync(agentsDir)) return mentionedAgents;
-
-    const existingAgents = new Set(
-      fs.readdirSync(agentsDir)
-        .filter((f) => f.endsWith(".ts") && !f.endsWith(".test.ts") && !f.endsWith(".d.ts") && f !== "index.ts" && f !== "base.ts")
-        .map((f) => f.replace(".ts", ""))
-    );
-
-    return mentionedAgents.filter((a) => !existingAgents.has(a) && !existingAgents.has(a.replace(/-agent$/, "")));
-  }
-
-  private formatIdeas(ideas: Idea[]): string {
-    if (ideas.length === 0) return "No improvement ideas generated.";
-    const lines: string[] = ["Improvement Ideas:", ""];
-    for (const idea of ideas) {
-      lines.push(`[${idea.source}|${idea.confidence.toFixed(2)}] ${idea.title} — ${idea.rationale}${idea.relatedReq ? ` (req: ${idea.relatedReq})` : ""}`);
-    }
-    return lines.join("\n");
+  mechanicalIdeate(projectPath: string) {
+    const engine = new IdeationEngine(projectPath);
+    return engine.runMechanical();
   }
 }