refactor(native-chat): remove the records-file and per-chat journal imports (#26038)

* refactor(native-chat): remove the records-file and per-chat journal imports

Every native chat user is on a build that already moved chat records and
history into the app-wide database, so the one-time copies are dead code:
the agent-sessions.json import and its owed-copy flag, the per-chat
journal.db import and the write-queue hold behind it, and the pre-SQLite
log.jsonl notice.

* refactor(native-chat): remove what only the deleted imports used

- JournalHostDatabase.unsyncedTransaction and the synchronous-pragma reset
  that undid it; JOURNAL_SYNCHRONOUS is now module-local. The stranded
  rollback test drives transaction() instead.
- deleteUnpublishedJournalRows and its SQL, plus its test.
- boundJournalStatusText.
- Stale comments naming the removed first-use copy (queued messages,
  send refusal example, JOURNAL_SYNCHRONOUS doc).
- Write-queue and readInOrder comments: a write also lags when issued
  behind one still waiting in line.
- Resolved-append ordering test binds the sink from inside a running read,
  so a resolver that read at handover now fails it.

* test(native-chat): run resolved-append in the SQLite runtime project

src/shared/agent-session-next-fence.ts

@@ -1,10 +1,10 @@
 // The only place a new fence number is chosen.
 //
-// Normally that is just "one past the current fence". For a record the one-time import took from
-// the records file's backup, or found beside a set-aside copy, it is not: the commit that never
-// landed may already have granted a fence the copy cannot show, and `isAgentSessionFenceCurrent`
-// compares with STRICT EQUALITY, so minting that exact number would hand a second writer a lease
-// the first one still believes it holds.
+// Normally that is just "one past the current fence". For a record an earlier build's one-time
+// import took from its records file's backup, or found beside a set-aside copy, it is not: the
+// commit that never landed may already have granted a fence the copy cannot show, and
+// `isAgentSessionFenceCurrent` compares with STRICT EQUALITY, so minting that exact number would
+// hand a second writer a lease the first one still believes it holds.
 //
 // Recovery records the floor instead of rewriting the current fence, because `live` means a handle
 // proven at exactly the current fence — moving it would invalidate the very records recovery exists

src/shared/agent-session-record.ts

@@ -119,10 +119,11 @@ export type AgentSessionLease = {
   /** True from load until the host adjudicates it; no writer is granted while set. */
   unreconciled: boolean
   /**
-   * Lowest fence a future grant may use. Set only when the records file's copy came from its backup,
-   * or sat beside a set-aside copy of the same chat: either may hide a fence already granted. The
-   * CURRENT fence is deliberately left alone: `live` means a handle proven at exactly that number,
-   * so rewriting it would invalidate the record it is trying to save.
+   * Lowest fence a future grant may use. Set only by an earlier build's import of its records file,
+   * when the copy came from its backup or sat beside a set-aside copy of the same chat: either may
+   * hide a fence already granted. The CURRENT fence is deliberately left alone: `live` means a
+   * handle proven at exactly that number, so rewriting it would invalidate the record it is trying
+   * to save.
    */
   minimumNextFence?: number
   /** Null on a released lease when nothing proved its owner gone. */