mbproxy: strip historical phase/wave/plan references from source comments

Comments described the *history* of how the code arrived (phase numbers,
wave IDs, review IDs, dated TODOs) instead of what it does today. That
scaffolding rotted as the codebase evolved. Cleaned 60 source files +
.gitignore; behaviour unchanged (387/387 tests still pass).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mbproxy/src/Mbproxy/Proxy/Multiplexing/UpstreamPipe.cs

@@ -49,12 +49,11 @@ internal sealed partial class UpstreamPipe : IAsyncDisposable
     // Internal CTS lets the multiplexer signal "drop this pipe now" without waiting for
     // the upstream socket to close cleanly.
     private readonly CancellationTokenSource _cts = new();
-    // Phase 12 (W2.2) — volatile so writes from DisposeAsync are observed by IsAlive /
-    // TrySendResponse on other threads without a fence.
+    // Volatile so writes from DisposeAsync are observed by IsAlive / TrySendResponse on
+    // other threads without a fence.
     private volatile bool _disposed;
 
-    // Phase 9: per-pipe forwarded-PDU counter (replaces the per-pair counter from the
-    // 1:1 model). Read by the status page.
+    // Per-pipe forwarded-PDU counter. Read by the status page.
     private long _pdusForwardedCount;
 
     /// <summary>Stable identity for status-page reporting and cascade cleanup.</summary>
@@ -227,11 +226,11 @@ internal sealed partial class UpstreamPipe : IAsyncDisposable
     }
 
     /// <summary>
-    /// Phase 12 (W1.3) — non-blocking response enqueue. Returns <c>true</c> when the frame
-    /// was queued for delivery, <c>false</c> when the pipe is dead OR the response channel
-    /// is full. Used by the per-PLC backend reader's fan-out loop so a single wedged
-    /// upstream cannot stall responses to peers sharing the same backend socket — without
-    /// this, a full <c>_responseChannel</c> on one pipe would block the reader task.
+    /// Non-blocking response enqueue. Returns <c>true</c> when the frame was queued for
+    /// delivery, <c>false</c> when the pipe is dead OR the response channel is full.
+    /// Used by the per-PLC backend reader's fan-out loop so a single wedged upstream
+    /// cannot stall responses to peers sharing the same backend socket — without this, a
+    /// full <c>_responseChannel</c> on one pipe would block the reader task.
     ///
     /// <para>A <c>false</c> return indicates the frame is the multiplexer's responsibility
     /// to drop and (optionally) account for via a counter. The wedged upstream's socket