Align SQLite feedback logs with feedback formatter (#13494)

## Summary
- store a pre-rendered `feedback_log_body` in SQLite so `/feedback`
exports keep span prefixes and structured event fields
- render SQLite feedback exports with timestamps and level prefixes to
match the old in-memory feedback formatter, while preserving existing
trailing newlines
- count `feedback_log_body` in the SQLite retention budget so structured
or span-prefixed rows still prune correctly
- bound `/feedback` row loading in SQL with the retention estimate, then
apply exact whole-line truncation in Rust so uploads stay capped without
splitting lines

## Details
- add a `feedback_log_body` column to `logs` and backfill it from
`message` for existing rows
- capture span names plus formatted span and event fields at write time,
since SQLite does not retain enough structure to reconstruct the old
formatter later
- keep SQLite feedback queries scoped to the requested thread plus
same-process threadless rows
- restore a SQL-side cumulative `estimated_bytes` cap for feedback
export queries so over-retained partitions do not load every matching
row before truncation
- add focused formatting coverage for exported feedback lines and parity
coverage against `tracing_subscriber`

## Testing
- cargo test -p codex-state
- just fix -p codex-state
- just fmt

codex author: `codex resume 019ca1b0-0ecc-78b1-85eb-6befdd7e4f1f`

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/state/src/model/log.rs

@@ -8,6 +8,7 @@ pub struct LogEntry {
     pub level: String,
     pub target: String,
     pub message: Option<String>,
+    pub feedback_log_body: Option<String>,
     pub thread_id: Option<String>,
     pub process_uuid: Option<String>,
     pub module_path: Option<String>,