feat(FN-1513): add skill selection resolver for deterministic session skills

- Add skill selection resolver for deterministic session skill sets
- Wire skill override into createKbAgent via AgentOptions
- Export skill resolver types and functions from engine index
- Add regression tests for skill override wiring and resolver fallback semantics
- Apply skill selection to triage and executor sessions
- Apply skill selection to reviewer, merger, and heartbeat sessions
- Fix SessionSkillContextInput to use AgentStore instead of TaskStore
- Add session-skill-context helper for unified skill selection across all session types
- Update memory with skill resolver diagnostics distinction

packages/engine/src/session-skill-context.test.ts

@@ -6,8 +6,7 @@ import {
   SKILL_DIAGNOSTIC_MESSAGES,
   type SessionPurpose,
 } from "./session-skill-context.js";
-import type { Agent } from "@fusion/core";
-import type { AgentStore } from "@fusion/core";
+import type { Agent, AgentStore } from "@fusion/core";
 
 describe("normalizeAgentSkills", () => {
   it("returns empty array for non-array input", () => {
@@ -92,11 +91,11 @@ describe("buildSessionSkillContextSync", () => {
 
   describe("assigned agent skills", () => {
     it("uses assigned agent skills when available", () => {
-      const agent: Agent = {
+      const agent = {
         id: "agent-001",
         name: "Test Agent",
-        role: "executor",
-        state: "idle",
+        role: "executor" as const,
+        state: "idle" as const,
         metadata: { skills: ["triage", "executor"] },
       } as unknown as Agent;
 

packages/engine/src/session-skill-context.ts

@@ -29,8 +29,7 @@
  * - Results are deduplicated preserving stable insertion order
  */
 
-import type { Agent } from "@fusion/core";
-import type { AgentStore } from "@fusion/core";
+import type { Agent, AgentStore } from "@fusion/core";
 import type { SkillSelectionContext } from "./skill-resolver.js";
 
 // ── Types ───────────────────────────────────────────────────────────────────