docs(codex): default to daemon-backed enforcement

[fafaisland]

Summary

• make Codex managed-preferences installer default to remote daemon mode with fail-closed unknown handling
• update Codex config examples and README to recommend dashboard-visible enforcement through permit0 serve --ui
• keep Claude Code, Codex, and OpenClaw positioned as supported integrations in the top-level README
• make Gmail and Outlook MCP READMEs explicitly document both Codex and Claude Code hook setup
• clarify that Gmail and Outlook MCP servers are plain MCP and enforcement happens at the host hook layer
• fix dashboard audit listing fallback so persisted decisions show after the in-memory audit sink is empty or reset

Tests

• bash -n integrations/permit0-codex/examples/install-managed-prefs.sh scripts/test-managed-prefs-roundtrip.sh scripts/test-codex-hook.sh
• python3 -m json.tool integrations/permit0-codex/examples/hooks.json.example >/dev/null
• PERMIT0=./target/debug/permit0 scripts/test-codex-hook.sh
• cargo test -p permit0-cli codex
• scripts/test-managed-prefs-roundtrip.sh
• cargo test -p permit0-ui