fix(codex): add persistent_instructions to baseline and relax sanity check

The global sanity check (check-codex-global-state.sh) hard-fails when
persistent_instructions is missing from ~/.codex/config.toml, but neither
the baseline .codex/config.toml nor the sync script ever define this field.
This causes a clean install to report a failing sanity check even though the
sync otherwise succeeds (#967).

- Add persistent_instructions to the baseline .codex/config.toml so that
  users who cp the config get a working default.
- Downgrade the sanity check from fail to warn, since persistent_instructions
  is additive and optional — users who rely solely on AGENTS.md should not be
  blocked.

Fixes #967 (persistent_instructions part; context7 naming addressed by #970)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Signed-off-by: Lidang-Jiang <lidangjiang@gmail.com>

scripts/codex/check-codex-global-state.sh

@@ -89,7 +89,13 @@ fi
 if [[ -f "$CONFIG_FILE" ]]; then
   check_config_pattern '^multi_agent\s*=\s*true' "multi_agent is enabled"
   check_config_absent '^\s*collab\s*=' "deprecated collab flag is absent"
-  check_config_pattern '^persistent_instructions\s*=' "persistent_instructions is configured"
+  # persistent_instructions is recommended but optional; warn instead of fail
+  # so users who rely on AGENTS.md alone are not blocked (#967).
+  if rg -n '^persistent_instructions\s*=' "$CONFIG_FILE" >/dev/null 2>&1; then
+    ok "persistent_instructions is configured"
+  else
+    warn "persistent_instructions is not set (recommended but optional)"
+  fi
   check_config_pattern '^\[profiles\.strict\]' "profiles.strict exists"
   check_config_pattern '^\[profiles\.yolo\]' "profiles.yolo exists"