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/os/os.ww

@@ -1,6 +1,5 @@
-// os — process and filesystem facade. The body of each call lands
-// either in libwwrt.a (rt_syscall trampoline) or libc bindings,
-// depending on how the program was linked.
+// The body of each call lands either in libwwrt.a (rt_syscall
+// trampoline) or libc bindings, depending on how the program was linked.
 
 package os;
 
@@ -155,10 +154,8 @@ export fn close(fd: i32) i32 = {
 	return syscall1(nr.CLOSE, fd: i64): i32;
 };
 
-// dup2(2): make `newfd` refer to the same description as `oldfd`,
-// closing `newfd` first if open. Returns `newfd` on success or a
-// negative errno. Used by w6c_ww to redirect stdout into an output
-// file without changing the cgen emit path.
+// Used by w6c_ww to redirect stdout into an output file without
+// changing the cgen emit path.
 export fn dup2(oldfd: i32, newfd: i32) i32 = {
 	return syscall2(nr.DUP2, oldfd: i64, newfd: i64): i32;
 };
@@ -208,9 +205,8 @@ export fn tryopen(path: str, flags: flag, mode: i32) (i32 | oserror) = {
 	return fd;
 };
 
-// lseek — set/inspect the fd's position. Returns the new offset or
-// a negative errno. We use this for fstat-free file-size discovery
-// (open ⇒ lseek to end ⇒ lseek back).
+// Used for fstat-free file-size discovery (open ⇒ lseek to end ⇒
+// lseek back).
 export fn lseek(fd: i32, off: i64, w: whence) i64 = {
 	return syscall3(nr.LSEEK, fd: i64, off, (w as i32): i64);
 };
@@ -273,7 +269,6 @@ export fn strerror(err: errno) str = {
 	return "Unknown error";
 };
 
-// filesize — byte length of an open fd via lseek-to-end-and-back.
 export fn filesize(fd: i32) (i64 | oserror) = {
 	let end: i64 = lseek(fd, 0i64, whence.END);
 	if (end < 0) { return end: oserror; };
@@ -282,9 +277,8 @@ export fn filesize(fd: i32) (i64 | oserror) = {
 	return end;
 };
 
-// readall — keep reading until `n` bytes have arrived or the fd
-// closes early. Hare name (io::readall); the buffer is caller-
-// supplied, matching the Plan 9 subset convention.
+// Hare name (io::readall); the buffer is caller-supplied, matching
+// the Plan 9 subset convention.
 export fn readall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
 	let got: u64 = 0u64;
 	for (got < n) {
@@ -296,8 +290,7 @@ export fn readall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
 	return got: i64;
 };
 
-// writeall — keep writing until `n` bytes have been accepted or the
-// fd refuses progress. Hare name (io::writeall).
+// Hare name (io::writeall).
 export fn writeall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
 	let sent: u64 = 0u64;
 	for (sent < n) {
@@ -309,8 +302,6 @@ export fn writeall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
 	return sent: i64;
 };
 
-// ---- process and filesystem helpers used by the `ww` driver ----------
-
 // access(2): returns 0 if the file is reachable, negative errno
 // otherwise. mode is the bitset described in <unistd.h> (F_OK=0).
 // Mirrors Hare's os::access (ref/hare/os/+linux/fs.ha:access).
@@ -531,8 +522,6 @@ export fn getdents64(fd: i32, buf: *u8, n: u64) i64 = {
 	return syscall3(nr.GETDENTS64, fd: i64, buf: i64, n: i64);
 };
 
-// ---- environment ------------------------------------------------------
-
 // rt_envp — runtime-side getter. rt/start.s captures envp into a DATAW
 // slot before calling main; this binding lifts the captured pointer
 // into ww. Same FFI shape as rt_syscall / rt_malloc / rt_abort: a TEXT
@@ -688,8 +677,6 @@ export fn args() []str = {
 	return r;
 };
 
-// ---- stat / lstat / fstat / exists -----------------------------------
-//
 // Ports of Hare's stat family (ref/hare/fs/fs.ha:172,196 +
 // ref/hare/sys/+linux/stat.ha:24-58). The Hare surface returns
 // `filestat` by value; ww's cgreturn ABI tops out at 24B today (see
@@ -830,8 +817,7 @@ type kstat = struct {
 let emptypath: [1]u8 = [0u8];
 
 // fillfilestat — copy a 144B kstat into the 80B Hare-shaped
-// filestat. Internal helper used by all three public entry points.
-// Mirrors Hare's st_to_filestat (ref/hare/os/+linux/dirfdfs.ha:259):
+// filestat. Mirrors Hare's st_to_filestat (ref/hare/os/+linux/dirfdfs.ha:259):
 // newfstatat populates every field, so the mask is the OR-fold of
 // all seven Hare stat_mask bits.
 fn fillfilestat(out: *filestat, k: *kstat) void = {