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/logger.ts

@@ -42,6 +42,3 @@ export function createLogger(prefix: string): Logger {
     },
   };
 }
-
-/** Logger for the plugin loader subsystem. */
-export const pluginLoaderLog = createLogger("plugin-loader");