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/bufio/stream_test.ww

@@ -1,8 +1,6 @@
-// streamtest — exercises the lib/bufio buffered stream surface. The
-// stream @tests are one scenario per fn. #94 fold-eFinal: the unified
-// value-return surface — `let st = memio.fixed(buf); &st.vt` into the
-// stream init, io.read/write/close return size/io.error. Row
-// ownership mirrors ref/hare/bufio/stream_test+test.ha.
+// Row ownership mirrors ref/hare/bufio/stream_test+test.ha.
+// Streams are built as `let st = memio.fixed(buf); &st.vt` — the #94
+// unified value-return io surface (read/write/close return size/io.error).
 
 package bufio_test;
 
@@ -10,8 +8,6 @@ import bufio;
 import io;
 import memio;
 
-// sputstr — copy the bytes of `s` into `into` starting at `off`,
-// returning the new offset.
 fn sputstr(s: str, into: []u8, off: i32) i32 = {
 	let i: i32 = 0;
 	for (i < s.len) {