Add native Guardian permission policy (DCO-clean)

[gagan114662]

Summary

• add owner-configurable Monitor and Lockdown permission policies for managed agents
• enforce fail-closed ACP permission handling with redacted decision evidence and unsupported-runtime fallback
• integrate local Numbat findings, lifecycle retention, race-safe turn cancellation, and accessible owner-facing policy controls
• replace Add native Guardian permission policy #4155 with one DCO-clean signed commit directly based on upstream main; no shared history was rewritten

Exact candidate

091998ca357043dea2c0cc3831a575740dfcd6b6

Verification at exact candidate

• cargo fmt --manifest-path desktop/src-tauri/Cargo.toml --all -- --check
• cargo check --manifest-path desktop/src-tauri/Cargo.toml
• full Tauri suite: 2,106 passed, 0 failed, 14 intentional OS-keychain ignores
• mixer diagnostics: 3/3 passed
• desktop repository checks: passed
• desktop tests: 3,911 passed, 0 failed
• desktop TypeScript: passed
• desktop production build: passed
• git diff --check: passed
• matching human Co-authored-by and Signed-off-by trailers

The first sandboxed Tauri run reported 17 localhost-bind permission failures; the unchanged suite passed completely when rerun with localhost permission. Stale reproducible build caches were removed after an out-of-disk interruption; no source or commit was deleted.

Originating Buzz channel: 2db0f46d-71e4-46c2-9798-3b248dac5fff