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

@@ -204,24 +204,27 @@ export async function buildSessionSkillContext(
     }
   }
 
-  // Rule 2: Use role fallback skills
+  return resolveRoleFallback(sessionPurpose, projectRootDir);
+}
+
+function resolveRoleFallback(
+  sessionPurpose: SessionPurpose,
+  projectRootDir: string,
+): SessionSkillContextResult {
   const roleFallbackSkills = getRoleFallbackSkills(sessionPurpose);
 
   if (roleFallbackSkills && roleFallbackSkills.length > 0) {
-    const skillSelectionContext: SkillSelectionContext = {
-      projectRootDir,
-      requestedSkillNames: roleFallbackSkills,
-      sessionPurpose,
-    };
-
     return {
-      skillSelectionContext,
+      skillSelectionContext: {
+        projectRootDir,
+        requestedSkillNames: roleFallbackSkills,
+        sessionPurpose,
+      },
       resolvedSkillNames: roleFallbackSkills,
       skillSource: "role-fallback",
     };
   }
 
-  // Rule 3: No skills available
   return {
     skillSelectionContext: undefined,
     resolvedSkillNames: [],
@@ -263,27 +266,5 @@ export function buildSessionSkillContextSync(
     }
   }
 
-  // Rule 2: Use role fallback skills
-  const roleFallbackSkills = getRoleFallbackSkills(sessionPurpose);
-
-  if (roleFallbackSkills && roleFallbackSkills.length > 0) {
-    const skillSelectionContext: SkillSelectionContext = {
-      projectRootDir,
-      requestedSkillNames: roleFallbackSkills,
-      sessionPurpose,
-    };
-
-    return {
-      skillSelectionContext,
-      resolvedSkillNames: roleFallbackSkills,
-      skillSource: "role-fallback",
-    };
-  }
-
-  // Rule 3: No skills available
-  return {
-    skillSelectionContext: undefined,
-    resolvedSkillNames: [],
-    skillSource: "none",
-  };
+  return resolveRoleFallback(sessionPurpose, projectRootDir);
 }