chore: comments say what the code does, not which task produced it

A comment that reads "MUST stay in lockstep with TryGetActiveCrossfade (K8)"
helps nobody outside the plan that used to have a K8 in it, and the plans are
not in this repo. Same for "Spec FR-4", "plan §B.2", "Sub-Task 4.4" and the
F/R/M/A/S round codes scattered through the style engine and the self-tests.

Personal names go too. "tester feedback from Jin (v1.4.7)" and "Flo decision
2026-06-15" carry the reason fine without naming anyone -- the version and the
reason are the parts a reader can act on, and a public repo should not need a
cast list to be read.

The rule applied throughout: keep the why, drop the reference. Version numbers
stay, since those resolve through the changelog. 77 files.

ChunkUtil also carried 281 lines of commented-out code -- an older ToChunks
variant and two helpers with no callers, inherited and never removed. Deleted;
git remembers them.

HellionChat/Infrastructure/Hosting/InitHostedServices.cs

@@ -135,7 +135,7 @@ internal sealed class PayloadHandlerInitHostedService(
 {
     public async Task StartAsync(CancellationToken cancellationToken)
     {
-        // §6.2 cycle-resolution: both singletons exist by the time HostedServices
+        // Cycle resolution: both singletons exist by the time HostedServices
         // run, so this is the first safe point to wire the setter.
         messageList.AttachPayloadHandler(payloadHandler);
 
@@ -172,7 +172,7 @@ internal sealed class PayloadHandlerInitHostedService(
 // InputBar -> CommandHelpWindow -> MainWindow -> InputBar (MS.DI does not catch
 // it through FactoryCallSite registrations and the resolve recurses silently).
 // Both singletons exist by host.StartAsync time, so this is the first safe point
-// to wire the setter — same §6.2 pattern as MessageList.AttachPayloadHandler.
+// to wire the setter — same setter-injection pattern as MessageList.AttachPayloadHandler.
 internal sealed class CommandHelpWindowInitHostedService(
     CommandHelpWindow commandHelpWindow,
     MainWindow mainWindow
@@ -190,7 +190,7 @@ internal sealed class CommandHelpWindowInitHostedService(
 // Attaches the singleton PayloadHandler to every pre-allocated pop-out
 // window's MessageList post-container-build. Pool/window cannot take the
 // PayloadHandler via ctor (that would close the silent FactoryCallSite cycle —
-// same §6.2 reason as MessageList.AttachPayloadHandler / CommandHelpWindow.
+// same setter-injection reason as MessageList.AttachPayloadHandler / CommandHelpWindow.
 // AttachMainWindow). Both singletons exist by host.StartAsync time.
 internal sealed class ChannelPopoutInitHostedService(
     ChannelPopoutPool pool,