Fix misleading WindowManager struct comment

The original comment said "Manages tumbling window boundaries" which
implied it only handled tumbling windows. Updated to reflect that it
handles both tumbling and sliding windows, and clarified the
slide_interval_ms field comment to distinguish the two cases.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: zzylol

asap-query-engine/src/precompute_engine/window_manager.rs

@@ -1,9 +1,13 @@
-/// Manages tumbling window boundaries and detects which windows have closed
-/// based on watermark advancement.
+/// Manages tumbling and sliding window boundaries and detects which windows
+/// have closed based on watermark advancement.
+///
+/// Tumbling windows are a special case where `slide_interval == window_size`.
+/// The same logic handles both — no separate code paths.
 pub struct WindowManager {
     /// Window size in milliseconds.
     window_size_ms: i64,
-    /// Slide interval in milliseconds (== window_size_ms for tumbling windows).
+    /// Slide interval in milliseconds. Equal to `window_size_ms` for tumbling
+    /// windows; strictly less than `window_size_ms` for sliding windows.
     slide_interval_ms: i64,
 }