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/types/config.ts

@@ -1,4 +1,5 @@
 import { BackendConfigSection } from "../backends/types.js";
+import { IdeationConfig, IdeationCategory } from "./ideation.js";
 
 export type AutonomyLevel = "full" | "supervised" | "guided";
 
@@ -82,6 +83,7 @@ export interface ProjectEntry {
 export interface CIAgentConfig {
   projects: ProjectEntry[];
   active_project: string;
+  active_projects: string[];
   autonomy: AutonomyConfig;
   model_profile: ModelProfile;
   parallelization: ParallelizationConfig;
@@ -90,11 +92,13 @@ export interface CIAgentConfig {
   git: GitConfig;
   backend: BackendConfigSection;
   gitea?: GiteaConfig;
+  ideation?: IdeationConfig;
 }
 
 export const DEFAULT_CIAGENT_CONFIG: CIAgentConfig = {
   projects: [],
   active_project: "",
+  active_projects: [],
   autonomy: {
     level: "full",
     escalation_hooks: ["deploy", "delete_data", "merge_to_main"],
@@ -165,4 +169,23 @@ export const DEFAULT_CIAGENT_CONFIG: CIAgentConfig = {
     owner: "",
     repo: "",
   },
+  ideation: {
+    enabled: true,
+    categories: ["security", "quality", "architecture", "coverage", "improvement"] as IdeationCategory[],
+    confidence_threshold: 0.6,
+    max_ideas: 20,
+    external_signals: {
+      npm_audit: true,
+      osv_advisories: true,
+      dependency_staleness: true,
+    },
+    cross_project: {
+      enabled: false,
+      similarity_weight: 0.5,
+    },
+    chaos: {
+      enabled: true,
+      scenarios: ["backend_unavailable", "requirement_change", "test_coverage_drop"],
+    },
+  },
 };