refactor: low-regret cleanup across core, engine, dashboard

- core: extract ai-engine-loader.ts to share @fusion/engine dynamic-import
  boilerplate between ai-summarize and memory-compaction (incl. AgentMessage
  type); collapse getInbox/getOutbox, listInsights/countInsights,
  listRuns/countRuns, and three hasProjectDb* variants behind shared helpers.
- core: drop unused pluginLoaderLog export; tighten two `any` casts
  (db.walCheckpoint row, plugin-loader error.code).
- engine: extract resolveRoleFallback helper from buildSessionSkillContext/Sync;
  remove 22 stale `eslint-disable no-explicit-any` directives across
  project-engine, self-healing, triage, worktree-pool.
- dashboard: apply ESLint autofix (let→const, empty `interface extends`→type).

All three packages: typecheck clean, full test suites pass (14,414 tests),
builds clean. Net lint: -31 warnings. No public behavior changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core/src/ai-engine-loader.ts

@@ -0,0 +1,45 @@
+/**
+ * Shared lazy loader for `@fusion/engine`'s `createKbAgent`.
+ *
+ * @fusion/engine must be imported dynamically (not statically) so that:
+ *   - core can be consumed in test environments where engine isn't resolvable
+ *   - a missing engine package fails soft instead of breaking module load
+ *
+ * Using a variable module specifier also prevents bundlers (Vite) from
+ * statically analysing and trying to resolve the import at build time.
+ */
+
+// Engine exports a function type we intentionally don't pull in here — importing
+// the type would reintroduce the static resolution this module is designed to avoid.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type CreateKbAgent = any;
+
+let createKbAgent: CreateKbAgent | undefined;
+
+async function initEngine(): Promise<void> {
+  try {
+    const engineModule = "@fusion/engine";
+    const engine = await import(/* @vite-ignore */ engineModule);
+    createKbAgent = engine.createKbAgent;
+  } catch {
+    createKbAgent = undefined;
+  }
+}
+
+/** Shape of a message in an agent session's state. */
+export interface AgentMessage {
+  role: string;
+  content?: string | Array<{ type: string; text: string }>;
+}
+
+/** Promise that resolves once the initial load attempt has completed. */
+const engineReady: Promise<void> = initEngine();
+
+/**
+ * Returns `createKbAgent` from `@fusion/engine`, or `undefined` if the engine
+ * could not be loaded (typical in tests or when engine isn't installed).
+ */
+export async function getKbAgent(): Promise<CreateKbAgent> {
+  await engineReady;
+  return createKbAgent;
+}