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/tests/Mbproxy.Tests/Proxy/Multiplexing/UpstreamPipeTests.cs

@@ -9,8 +9,8 @@ namespace Mbproxy.Tests.Proxy.Multiplexing;
 
 /// <summary>
 /// Unit tests for <see cref="UpstreamPipe"/>'s response-channel contract — particularly
-/// the Phase 12 (W1.3) <see cref="UpstreamPipe.TrySendResponse"/> non-blocking enqueue
-/// added so the per-PLC backend reader cannot be stalled by one slow upstream client.
+/// the <see cref="UpstreamPipe.TrySendResponse"/> non-blocking enqueue, which exists
+/// so the per-PLC backend reader cannot be stalled by one slow upstream client.
 /// </summary>
 [Trait("Category", "Unit")]
 public sealed class UpstreamPipeTests
@@ -40,7 +40,7 @@ public sealed class UpstreamPipeTests
     // ── Tests ─────────────────────────────────────────────────────────────────
 
     /// <summary>
-    /// W1.3 — when no write-loop is draining the response channel, repeated
+    /// When no write-loop is draining the response channel, repeated
     /// <see cref="UpstreamPipe.TrySendResponse"/> calls must succeed up to the channel's
     /// bounded capacity and return <c>false</c> on every subsequent call without blocking.
     /// This is the non-blocking contract the per-PLC backend reader relies on.
@@ -80,7 +80,7 @@ public sealed class UpstreamPipeTests
     }
 
     /// <summary>
-    /// W1.3 — once the pipe has been disposed, <see cref="UpstreamPipe.TrySendResponse"/>
+    /// Once the pipe has been disposed, <see cref="UpstreamPipe.TrySendResponse"/>
     /// returns <c>false</c> regardless of channel state, never throws.
     /// </summary>
     [Fact]