Add sort_by ordering for the log viewer, with a missing-param fallback/drop toggle (ticket 045)

/api/logs now accepts sort_by (an already-declared param name) and
sort_missing_fallback: lines carrying that param are ordered by its value,
while lines missing it are either appended in ottyl_seq order (fallback,
the default) or dropped from the response. Default ottyl_ts-tracking
order is unchanged when sort_by is omitted.

The log viewer (both the inline panel and its popout) exposes this as a
"Sort by" control next to the column picker, persisted to localStorage
under one shared key (ottyl.logPreview.sort) — the same global-viewer-
setting convention already used for visible param columns and the log
viewer's height, since there's no per-dashboard scope for this to divide
by.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

src/api.rs

@@ -1527,4 +1527,52 @@ mod tests {
         let (_, body) = get_json(&app, "/api/logs").await;
         assert_eq!(body.as_array().unwrap().len(), 3);
     }
+
+    /// Ticket 045: seeded fixture mixing lines that carry the sort param with lines that don't,
+    /// exercised through the actual HTTP endpoint rather than just `handle_query` directly.
+    #[tokio::test]
+    async fn get_logs_sort_by_orders_by_param_and_toggles_missing_param_handling() {
+        let (app, engine, _settings, _dir) = test_app();
+
+        declare_test_param(&app, "priority", r"priority=(?P<priority>\d+)", "priority", "number").await;
+
+        ingest_lines(
+            &engine,
+            0,
+            &[
+                "priority=3 boom", // sequence 0, has param
+                "no param here",   // sequence 1, missing
+                "priority=1 boom", // sequence 2, has param
+                "also missing",    // sequence 3, missing
+            ],
+        )
+        .await;
+
+        // Default order (no sort_by): unchanged, plain ingest/ottyl_seq order.
+        let (status, body) = get_json(&app, "/api/logs").await;
+        assert_eq!(status, StatusCode::OK);
+        let sequences: Vec<u64> = body.as_array().unwrap().iter().map(|e| e["sequence"].as_u64().unwrap()).collect();
+        assert_eq!(sequences, vec![0, 1, 2, 3]);
+
+        // sort_by=priority with the fallback toggle on (the default): entries carrying the param
+        // sorted ascending by its value, then the missing-param entries ordered by ottyl_seq.
+        let (status, body) = get_json(&app, "/api/logs?sort_by=priority").await;
+        assert_eq!(status, StatusCode::OK);
+        let sequences: Vec<u64> = body.as_array().unwrap().iter().map(|e| e["sequence"].as_u64().unwrap()).collect();
+        assert_eq!(sequences, vec![2, 0, 1, 3]);
+
+        // Same sort_by, but with the fallback toggle explicitly off: missing-param lines are dropped.
+        let (status, body) = get_json(&app, "/api/logs?sort_by=priority&sort_missing_fallback=false").await;
+        assert_eq!(status, StatusCode::OK);
+        let sequences: Vec<u64> = body.as_array().unwrap().iter().map(|e| e["sequence"].as_u64().unwrap()).collect();
+        assert_eq!(sequences, vec![2, 0]);
+    }
+
+    #[tokio::test]
+    async fn get_logs_sort_by_unknown_param_returns_400() {
+        let (app, _engine, _settings, _dir) = test_app();
+        let (status, body) = get_json(&app, "/api/logs?sort_by=does_not_exist").await;
+        assert_eq!(status, StatusCode::BAD_REQUEST);
+        assert!(body["error"].as_str().unwrap().contains("does_not_exist"));
+    }
 }