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/strconv/strconv.ww

@@ -1,5 +1,3 @@
-// strconv — number↔string conversions.
-//
 // Mirrors Hare's strconv:: surface. The *tos functions return a
 // `const str` view into a module-level buffer that is overwritten on
 // the next call to the same function; callers must copy the bytes if
@@ -71,7 +69,7 @@ let lut_lower: [16]rune = [
 // fidelity; the initial value is irrelevant (only the freshly-written
 // prefix is ever read) but the fill form is exercised (probed: emits
 // byte-identically cross-stage).
-let u64tos_buf: [64]u8 = [0...];	// 64 binary digits
+let u64tos_buf: [64]u8 = [0...];
 
 // u64tos — convert u to a base-b numeric string. Returns a view into
 // `u64tos_buf`, overwritten on the next call; copy via strings.dup to
@@ -114,7 +112,7 @@ export fn u64tos(u: u64, b: base) str = {
 // i64tos_buf — independent from u64tos_buf so i64tos's own u64tos call
 // (the magnitude) doesn't clobber the in-flight result. 65 = 64 digits
 // plus the leading '-'. Hare's `static let buf: [65]u8` (itos.ha:18).
-let i64tos_buf: [65]u8 = [0...];	// 64 binary digits plus '-'
+let i64tos_buf: [65]u8 = [0...];
 
 // i64tos — convert i to a base-b numeric string. Returns a view into
 // `i64tos_buf`. Verbatim port of ref/hare/strconv/itos.ha:10-32.