app-server: source /feedback logs from sqlite at trace level (#12969)

## Summary
- write app-server SQLite logs at TRACE level when SQLite is enabled
- source app-server `/feedback` log attachments from SQLite for the
requested thread when available
- flush buffered SQLite log writes before `/feedback` queries them so
newly emitted events are not lost behind the async inserter
- include same-process threadless SQLite rows in those `/feedback` logs
so the attachment matches the process-wide feedback buffer more closely
- keep the existing in-memory ring buffer fallback unchanged, including
when the SQLite query returns no rows

## Details
- add a byte-bounded `query_feedback_logs` helper in `codex-state` so
`/feedback` does not fetch all rows before truncating
- scope SQLite feedback logs to the requested thread plus threadless
rows from the same `process_uuid`
- format exported SQLite feedback lines with the log level prefix to
better match the in-memory feedback formatter
- add an explicit `LogDbLayer::flush()` control path and await it in
app-server before querying SQLite for feedback logs
- pass optional SQLite log bytes through `codex-feedback` as the
`codex-logs.log` attachment override
- leave TUI behavior unchanged apart from the updated `upload_feedback`
call signature
- add regression coverage for:
  - newest-within-budget ordering
  - excluding oversized newest rows
  - including same-process threadless rows
  - keeping the newest suffix across mixed thread and threadless rows
  - matching the feedback formatter shape aside from span prefixes
  - falling back to the in-memory snapshot when SQLite returns no logs
  - flushing buffered SQLite rows before querying

## Follow-up
- SQLite feedback exports still do not reproduce span prefixes like
`feedback-thread{thread_id=...}:`; there is a `TODO(ccunningham)` in
`codex-rs/state/src/log_db.rs` for that follow-up.

## Testing
- `cd codex-rs && cargo test -p codex-state`
- `cd codex-rs && cargo test -p codex-app-server`
- `cd codex-rs && just fmt`

codex-rs/feedback/src/lib.rs

@@ -226,6 +226,7 @@ impl CodexLogSnapshot {
         include_logs: bool,
         extra_log_files: &[PathBuf],
         session_source: Option<SessionSource>,
+        logs_override: Option<Vec<u8>>,
     ) -> Result<()> {
         use std::collections::BTreeMap;
         use std::fs;
@@ -310,7 +311,7 @@ impl CodexLogSnapshot {
 
         if include_logs {
             envelope.add_item(EnvelopeItem::Attachment(Attachment {
-                buffer: self.bytes.clone(),
+                buffer: logs_override.unwrap_or_else(|| self.bytes.clone()),
                 filename: String::from("codex-logs.log"),
                 content_type: Some("text/plain".to_string()),
                 ty: None,