fix(examples): redact tokens with python literal-string replace, not sed

The sed-based redact_log in demo.sh broke when one of the auth tokens
contained a character that conflicted with sed's pattern parser
("unterminated substitute pattern" on the Codex JWT). The whole log
tail then blanks on failure, hiding the very failure context we're
trying to surface.

Switch to a python subprocess that takes the tokens via argv and does
literal str.replace. No regex, no delimiter games, no truncation.

Signed-off-by: Alexander Watson <zredlined@gmail.com>

Author: zredlined

examples/agent-driven-policy-management/demo.sh

@@ -120,13 +120,25 @@ spin_clear() {
 # Redact host-side credentials from the agent log tail before printing on
 # failure. Codex shouldn't echo the token, but a misbehaving tool call (e.g.,
 # `curl -v`) could leak it; sanitize before showing the log.
+#
+# Uses python's literal `str.replace` rather than sed because tokens
+# (especially JWTs) can contain characters that break sed's pattern parser
+# — a sed delimiter collision in one of the substitutions blanks the entire
+# log tail, hiding the very failure context we're trying to surface.
 redact_log() {
-    local replacement='[redacted]'
-    sed \
-        -e "s|${DEMO_GITHUB_TOKEN:-__no_github_token__}|${replacement}|g" \
-        -e "s|${CODEX_AUTH_ACCESS_TOKEN:-__no_codex_access__}|${replacement}|g" \
-        -e "s|${CODEX_AUTH_REFRESH_TOKEN:-__no_codex_refresh__}|${replacement}|g" \
-        -e "s|${CODEX_AUTH_ACCOUNT_ID:-__no_codex_account__}|${replacement}|g"
+    python3 - \
+        "${DEMO_GITHUB_TOKEN:-}" \
+        "${CODEX_AUTH_ACCESS_TOKEN:-}" \
+        "${CODEX_AUTH_REFRESH_TOKEN:-}" \
+        "${CODEX_AUTH_ACCOUNT_ID:-}" \
+        <<'PY'
+import sys
+tokens = [t for t in sys.argv[1:] if t]
+for line in sys.stdin:
+    for t in tokens:
+        line = line.replace(t, "[redacted]")
+    sys.stdout.write(line)
+PY
 }
 
 fail() {