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/Ui/Components/InputBar.cs

@@ -118,7 +118,7 @@ internal sealed class InputBar
     // Note: when MainWindow is closed, DrawInputField never runs, so
     // _isFocused keeps the last value written by the previous draw pass.
     // The consumer that actually pushes this state across the IPC boundary
-    // (TypingIpc.BuildState, see F3 Step 2) gates on Plugin.MainWindow.IsOpen
+    // (TypingIpc.BuildState) gates on Plugin.MainWindow.IsOpen
     // itself, so the stale backing-field never leaks to subscribers. Mirroring
     // the gate here would require an extra Plugin-backref in InputBar that the
     // rest of the component doesn't need.
@@ -1183,7 +1183,7 @@ internal sealed class InputBar
 }
 
 // DTO for an in-flight auto-translate completion. Lives as a companion type
-// in this file because it is only consumed by InputBar (see v1.7.1 Fix #4 plan §2.4).
+// in this file because it is only consumed by InputBar.
 internal sealed class AutoCompleteInfo
 {
     // ToComplete MUST be a mutable field (not an auto-property), because the