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

selfhost/, cmd/, internal/ join the tree-wide sweep: every section
banner dies (91 selfhost + the cmd C-style dividers -> 0); narration
and stale contracts deleted (pre-#22 bundler notes, retired
single-PT_LOAD and no-archive claims, superseded ABI tables); every
ref/harec/qbe cite, task cite, encoding/ELF contract, and rule-10
twin pointer kept; lost lifetime/rationale lines restored where the
sweep over-cut (elf_globals ownership, kwtab linear-scan). Comment-
only proven: all five wwstage tool binaries byte-identical across
the sweep; test-commit, test-byteid (161+1399, 0 pinned-divergent),
and test-bootstrap (fixed point + 991-995 byte-id) all exit 0.
The read-through banked 66 latent-bug leads (checkpoint).

selfhost/cmd/wcc/err.ww

@@ -1,7 +1,6 @@
-// selfhost/cmd/wcc/err.ww — port of cmd/wcc/err.c.
-//
-// Diagnostics. Plan 9 style: short, no levels beyond fatal/error/warn.
-// Output goes through os.write so we don't pull in libc stdio.
+// Port of cmd/wcc/err.c. Plan 9 style: short, no levels beyond
+// fatal/error/warn. Output goes through os.write so we don't pull in
+// libc stdio.
 
 package wcc;