fix: avoid history reclamation during structure-only upgrades

Ordinary database schema upgrades previously ran VACUUM on free pages and
showed misleading history-cleanup progress. Separate structure upgrades from
required legacy conversions, retaining reclamation intent only for retries
within the same startup. Preserve released data without new schema versions
or persistent migration markers; Agent and normal writes remain unchanged.

Add real SQLite and Worker regressions, bilingual operation-specific startup
copy, and migration documentation. Synchronize native Electron drag input
with actual resize state without weakening layout assertions.

Validation: 47 focused migration tests passed; typecheck, lint and diff checks
passed. Final full suite: 5137 passed, 74 skipped, 2 unrelated Electron failures.
Both failing Electron tests passed an isolated rerun; full CI remains unverified.

Release note: 修复普通数据库结构升级再次整理历史和回收空间的问题；仅在需要转换旧数据时执行相关处理，启动页准确显示当前升级操作。

docs/features/magic-notes/progress.md

@@ -467,8 +467,13 @@ Electron cases with substituted model output; live-provider checks remain opt-in
   migration and backup requirements are defined in the
   [storage contract](./technical-design.md#file-storage-and-writes).
 - The startup worker converts one entry per transaction and verifies hydrated
-  readback before clearing the legacy payload. Reclamation checks the freelist
-  on every attempt, including retries after conversion has finished. Committed
+  readback before clearing the legacy payload. The original implementation checked
+  the freelist on every attempt. This was narrowed by the September 21 startup
+  fix and the September 26 structure-upgrade fix: only a required legacy
+  conversion enables reclamation, with its decision retained for same-startup
+  retries, not later launches. Current rules are in the
+  [migration contract](./technical-design.md#schema-38-migration).
+  Committed
   saves/deletes/resets remain successful when manifest or GC cleanup fails;
   failures are logged and cleanup is retried on later access or reopen.
 - Storage implementation handoff reports 135/135 focused tests passed across