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/ideation.ts

@@ -0,0 +1,105 @@
+export type IdeationSource =
+  | "uncovered_requirement"
+  | "repeated_lesson"
+  | "low_confidence_decision"
+  | "escalation_pattern"
+  | "compound_pattern"
+  | "partial_requirement"
+  | "gap_in_coverage"
+  | "improvement_pattern"
+  | "architecture_drift"
+  | "verification_inversion"
+  | "spec_ambiguity"
+  | "spec_contradiction"
+  | "spec_missing"
+  | "external_signal"
+  | "cross_project_lesson"
+  | "chaos_scenario";
+
+export type IdeationCategory =
+  | "security"
+  | "quality"
+  | "architecture"
+  | "coverage"
+  | "improvement"
+  | "spec"
+  | "chaos";
+
+export type IdeationAction =
+  | "add_requirement"
+  | "update_architecture"
+  | "update_roadmap"
+  | "fix_documentation"
+  | "add_test"
+  | "add_security_pattern"
+  | "refactor"
+  | "new_milestone_phase";
+
+export type IdeationTier = "mechanical" | "backend-enriched" | "cross-project";
+
+export interface Idea {
+  id: string;
+  source: IdeationSource;
+  category: IdeationCategory;
+  title: string;
+  rationale: string;
+  confidence: number;
+  relatedReq?: string;
+  actions: IdeationAction[];
+  tier: IdeationTier;
+}
+
+export interface IdeationResult {
+  project: string;
+  milestone: string;
+  ideas: Idea[];
+  summary: IdeationSummary;
+}
+
+export interface IdeationSummary {
+  total: number;
+  accepted: number;
+  skipped: number;
+  by_category: Record<string, number>;
+  by_tier: Record<string, number>;
+}
+
+export interface IdeationConfig {
+  enabled: boolean;
+  categories: IdeationCategory[];
+  confidence_threshold: number;
+  max_ideas: number;
+  external_signals: {
+    npm_audit: boolean;
+    osv_advisories: boolean;
+    dependency_staleness: boolean;
+  };
+  cross_project: {
+    enabled: boolean;
+    similarity_weight: number;
+  };
+  chaos: {
+    enabled: boolean;
+    scenarios: string[];
+  };
+}
+
+export const DEFAULT_IDEATION_CONFIG: IdeationConfig = {
+  enabled: true,
+  categories: ["security", "quality", "architecture", "coverage", "improvement"],
+  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"],
+  },
+};