lib: banner purge + WHY-only comment sweep (rule 8)

Every // ---- section banner dies (132 -> 0): names carry the WHAT.
Narration deleted (filename restatements, run-with lines, what-the-
next-line-does); every ref/hare cite, task cite, divergence, ABI/
layout contract, and ownership qualifier kept (borrowed-view lines
restored where the sweep over-cut). Comment-only proven: all 442
walk-workdir .s and 32 import-probe .s byte-identical before/after;
libbyteid 56-roster all-ID.

lib/io/io.ww

@@ -5,19 +5,13 @@
 // through it. The error channel is the return value — Hare-shaped
 // tagged unions instead of errno-style integer sentinels.
 //
-// This file owns the eof / underread variant tags; lib/io/stream.ww
-// owns the `vtable` + `stream` + read/write/close dispatchers,
-// lib/io/empty.ww owns the [[empty]] singleton, and lib/io/types.ww
-// owns the error union, mode/whence enums, and the reader/writer/
-// closer fn-type aliases.
 // #94 fold-eFinal collapsed the pre-vtable `stream` struct + `closed`
 // tag into the single vtable surface; the dispatchers are read/write/
 // close (over `stream`), final over `handle` at io fold-2 (#5).
 package io;
 
-// eof — read past the end of the stream. Hare uses the `done`
-// singleton for EOF; ww doesn't have `done` yet so we ship a
-// named-void variant tag. Lifts to `done` with #93.
+// Hare uses the `done` singleton for EOF; ww doesn't have `done` yet
+// so we ship a named-void variant tag. Lifts to `done` with #93.
 export type eof = void;
 
 // underread — an I/O handle hit eof partway through a fixed-size