feat: connect conversations with Magic Notes

Let users retain useful assistant replies or complete conversations without
leaving their chat workflow. Preview and edit captured text, choose an existing
note or atomically create a note with its first entry, and return to the source
conversation or message from saved records.

Add an application-scoped Notes workbar tab with title/body search and quick
text appends. Preserve drafts across conversation switches and guard closing,
replacement and disabling. Schema 48 stores optional source metadata without
rewriting file-backed bodies; source deletion retains the saved note. Older
clients cannot reopen an upgraded database without a pre-upgrade backup.

Release note: 可将助手回答或完整会话预览、编辑后加入魔法笔记，并从笔记返回原会话或消息。右侧快速笔记支持搜索和追加文字，切换会话保留草稿；采集本身不调用模型，保存后自动评论仍遵循已有设置。

Validation: isolated HEAD-based candidate passed 22 files / 930 focused tests,
plus 20 gateway tests after including its create-result fixture adjustment.
Real Electron App/preload/IPC/SQLite acceptance passed for all 502 historical
messages, exact-entry/source navigation, native keyboard input in a 214px
panel, reopen and source-deletion retention, with zero capture model calls.
Repository lint and web TypeScript passed. Cached whitespace and secret-pattern
checks passed; native-client changes and unrelated IPC extraction are excluded.

Validation limits: the isolated source tree reuses installed node_modules,
where a parallel task upgraded DSH from the committed 0.1.2-rc.1 to 0.1.7-rc.2.
Full typecheck reports 14 DSH errors in three unchanged files; the full-suite
attempt with --bail=1 also fails in deepseek-harness-host.test.ts. These are not
all-green repository or release-package results. Earlier execution-time full
suite failures and fixture repairs remain recorded in the feature progress doc.

FEATURES.md

@@ -674,6 +674,16 @@ records are listed separately and do not introduce another feature status.
   navigation can show the incomplete-todo count, and create, save, and comment
   results use application-wide notifications. Agent/MCP note writes automatically
   refresh the open workbench while preserving selection and unsaved drafts.
+- **Conversation capture and quick notes** (implemented; real Electron acceptance passed):
+  Preview and edit an assistant response or complete conversation text before
+  appending to an existing note or creating one with its first entry. The compact
+  Notes workbar tab supports title/body search, quick text appends and full-workspace
+  navigation. Saved sources link back to conversations and messages; drafts survive
+  conversation switches. Real App/preload/IPC/SQLite acceptance passed, including
+  complete 502-message history and native keyboard use in a 214px panel, with zero
+  model calls. Repository validation is not all green; the
+  [validation record](./docs/features/magic-notes/progress.md) separates focused
+  passes, fixture repairs and execution-time test/typecheck failures.
 - [x] **Paged canvas notes**: The integrated PeopleLib Fabric + Quill editor
   combines flowing body text with pen/highlighter, object selection/transforms,
   floating text, images and paper templates. Editors and read-only viewers support
@@ -696,13 +706,13 @@ records are listed separately and do not introduce another feature status.
   invalidated by layout changes and reanalyzed in after-save-auto mode. MCP
   rejects plain-text replacement of canvas entries. Implementation is complete;
   final validation status is tracked in the [feature progress record](./docs/features/magic-notes/progress.md).
-  The first upgrade migrates stored bodies into files and raises the database
-  schema to 39 together with attachment changes. Older clients cannot reopen
+  Historical body migration moved stored bodies into files; schema 48 now adds
+  conversation-source metadata. Older clients cannot reopen
   that database; rollback requires a pre-upgrade backup.
 - [ ] **MCP Server Control Plane** (planned): Unified MCP lifecycle, health
   checks, reconnection, schema cache, isolation, approval, and audit.
-- [ ] **Traceable note excerpts and AI editing** (planned): Collects sourced
-  excerpts from conversations, knowledge, and the web and provides
+- [ ] **Knowledge/web excerpts and AI editing** (planned): Extend capture beyond
+  the implemented conversation-text path to knowledge and web excerpts, with
   confirmation-based summarization, rewriting, and organization.
 
 ### Work management, long-term collaboration, and workflows