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/regex/regex_test.ww

@@ -564,8 +564,6 @@ type fdexp = struct {
 };
 
 
-// ---- fold 3: anchors / escape / postfix / alternation ----------------
-
 // instsig — flatten an inst for the table-driven program pins below:
 // kind base + payload. Takes the 56B inst by value (the #19-landed
 // is_consuming_inst shape).
@@ -821,8 +819,6 @@ type cerow = struct {
 	};
 };
 
-// ---- fold 4: bracket expressions --------------------------------------
-
 // Emitted-program pins for the `[..]` arm: the charset inst lands where
 // a literal would (and composes with fold-3's postfix/anchors), the
 // charsets table grows one entry per bracket, negation rides
@@ -1173,8 +1169,6 @@ type cscase = struct {
 	};
 };
 
-// ---- fold 5a: capture groups ------------------------------------------
-
 // The fold-5a compile-error surface, exact texts. ")" and "(" are
 // Hare's own ERROR fixtures (+test.ha:276/606); "a("/"a)" graduate
 // here from the metachar-loud table with their real texts. The
@@ -1464,8 +1458,6 @@ type smcase = struct {
 	};
 };
 
-// ---- fold 5b: repetition ----------------------------------------------
-
 // 5b compile-error rows end-to-end through compile() — the two
 // parse_repetition texts surface verbatim (+test.ha:461-463 ERROR
 // rows). "a{" is the GRADUATED metachar-loud row: with `{` ported the
@@ -1693,8 +1685,6 @@ type smcase = struct {
 	};
 };
 
-// ---- fold 6: POSIX character classes ---------------------------------
-
 // compile error: `[[:` with no valid class name
 // ref/hare/regex/+test.ha — no direct cite; error string from
 // regex.ha:203 "No character class after '[:'".