Add process_uuid to sqlite logs (#11534)

## Summary
This PR is the first slice of the per-session `/feedback` logging work:
it adds a process-unique identifier to SQLite log rows.

It does **not** change `/feedback` sourcing behavior yet.

## Changes
- Add migration `0009_logs_process_id.sql` to extend `logs` with:
  - `process_uuid TEXT`
  - `idx_logs_process_uuid` index
- Extend state log models:
  - `LogEntry.process_uuid: Option<String>`
  - `LogRow.process_uuid: Option<String>`
- Stamp each log row with a stable per-process UUID in the sqlite log
layer:
  - generated once per process as `pid:<pid>:<uuid>`
- Update sqlite log insert/query paths to persist and read
`process_uuid`:
  - `INSERT INTO logs (..., process_uuid, ...)`
  - `SELECT ..., process_uuid, ... FROM logs`

## Why
App-server runs many sessions in one process. This change provides a
process-scoping primitive we need for follow-up `/feedback` work, so
threadless/process-level logs can be associated with the emitting
process without mixing across processes.

## Non-goals in this PR
- No `/feedback` transport/source changes
- No attachment size changes
- No sqlite retention/trim policy changes

## Testing
- `just fmt`
- CI will run the full checks

codex-rs/state/src/log_db.rs

@@ -20,6 +20,7 @@
 
 use chrono::Duration as ChronoDuration;
 use chrono::Utc;
+use std::sync::OnceLock;
 use std::time::Duration;
 use std::time::SystemTime;
 use std::time::UNIX_EPOCH;
@@ -33,6 +34,7 @@ use tracing::span::Id;
 use tracing::span::Record;
 use tracing_subscriber::Layer;
 use tracing_subscriber::registry::LookupSpan;
+use uuid::Uuid;
 
 use crate::LogEntry;
 use crate::StateRuntime;
@@ -44,14 +46,19 @@ const LOG_RETENTION_DAYS: i64 = 90;
 
 pub struct LogDbLayer {
     sender: mpsc::Sender<LogEntry>,
+    process_uuid: String,
 }
 
 pub fn start(state_db: std::sync::Arc<StateRuntime>) -> LogDbLayer {
+    let process_uuid = current_process_log_uuid().to_string();
     let (sender, receiver) = mpsc::channel(LOG_QUEUE_CAPACITY);
     tokio::spawn(run_inserter(std::sync::Arc::clone(&state_db), receiver));
     tokio::spawn(run_retention_cleanup(state_db));
 
-    LogDbLayer { sender }
+    LogDbLayer {
+        sender,
+        process_uuid,
+    }
 }
 
 impl<S> Layer<S> for LogDbLayer
@@ -118,6 +125,7 @@ where
             target: metadata.target().to_string(),
             message: visitor.message,
             thread_id,
+            process_uuid: Some(self.process_uuid.clone()),
             module_path: metadata.module_path().map(ToString::to_string),
             file: metadata.file().map(ToString::to_string),
             line: metadata.line().map(|line| line as i64),
@@ -196,6 +204,15 @@ where
     thread_id
 }
 
+fn current_process_log_uuid() -> &'static str {
+    static PROCESS_LOG_UUID: OnceLock<String> = OnceLock::new();
+    PROCESS_LOG_UUID.get_or_init(|| {
+        let pid = std::process::id();
+        let process_uuid = Uuid::new_v4();
+        format!("pid:{pid}:{process_uuid}")
+    })
+}
+
 async fn run_inserter(
     state_db: std::sync::Arc<StateRuntime>,
     mut receiver: mpsc::Receiver<LogEntry>,