fix: reduce redundant work during chat and note startup

Avoid hidden activity renders, no-op message saves and attachment scans when pinning conversations. Reuse note body inspection and skip unchanged attachment reference writes while preserving recovery and cleanup behavior.

Skip unnecessary Markdown normalization and memoize subagent lookups without delaying live rich text. Add storage operation counts and real Electron rendering equivalence benchmarks; full-render speedup remains unproven.

Validation: 5397 tests passed, 84 skipped; typecheck passed. Lint passed excluding two existing untracked sidebar probe files.

Release note: Reduce repeated rendering and disk work during chat, conversation pinning and note startup while preserving existing content and interactions.

src/main/ipc.ts

@@ -6397,8 +6397,6 @@ export function registerIpcHandlers(
       assistantDatabase.setConversationPinned(
         conversationSetPinnedSchema.parse(input)
       )
-      contextManager.assets?.reconcile((conversationId, kind, ownerId) => assistantDatabase.hasAttachmentOwner(conversationId, kind, ownerId), false, contextManager.activeContextIds())
-      if (contextManager.assets) contextManager.cancelUnavailableImport()
       publishConversationChange()
     }
   )