fix(portability): make test green on macOS, GNU-only idioms replaced

The suite and seven libs assumed a GNU userland: `cmd | grep -q` under
pipefail (grep exits at the first match, the producer takes SIGPIPE,
rc 141 → 15 false "merged into" FAILs in gitflow-test), `sed -i` with no
suffix, `wc -l` padding compared as a string, `stat -c`, `touch -d`,
`realpath -m` (gstack-links refusal never fired), bare `timeout` off the
sanitized PATH (design gate READY BUT UNVERIFIED), `grep -oP` (update-all
emptied the plugin list). Thirteen suites were red on this machine.

Portable forms on the native userland of both OS: producer captured out
of the pipeline, `sed -i.bak` in tests and a temp-sibling `sed_profile`
on the user dotfile, `tr -d ' '`, python3 perms, `touch -t`, a
`realpath -m` emulation that refuses `..`, perl `alarm` for the 15 s
bound, `sed -n` token extraction. Regression tests: gstack-links T4b,
doctrine-citers Alphabet/Alpha flip, profile-set-managed T18 (failing CLI
no longer aborts `set`), new portability-census suite over the tracked
shell files. Linux run deferred (see TODO).

lib/tests/run-doc-commit.sh

@@ -101,7 +101,7 @@ printf '    err: %s\n' "$(printf '%s' "$ERR" | grep -i decisions | head -1)"
 if [ "$RC" -eq 4 ]; then ok "mixed → exit 4"; else ko "expected 4, got $RC"; fi
 if [ "$(git -C "$R" rev-parse HEAD)" = "$BEFORE" ]; then ok "NOTHING committed (README not half-committed)"; else ko "a commit slipped through"; fi
 if printf '%s' "$ERR" | grep -q '.claude/memory/decisions.md'; then ok "stderr names the offender"; else ko "offender not named"; fi
-if git -C "$R" status --porcelain | grep -q ' M README.md'; then ok "README left dirty (not embarked)"; else ko "README state wrong"; fi
+if grep -q ' M README.md' < <(git -C "$R" status --porcelain); then ok "README left dirty (not embarked)"; else ko "README state wrong"; fi
 rm -rf "$R"
 
 echo "T2 — dynamic pathspec: clean passed path filtered, no abort"