Archive legacy runtime internals

[jmcte]

Summary

• archive the browser bridge, native host bundle, helper scripts, and legacy Rust daemon/native-host internals under legacy/
• remove the active apw host CLI surface and simplify status --json to the native app broker status shape
• remove the active legacy parity CI/release gate and update docs/tests for the v2.1.0 archive boundary

Closes #47.

Stacked on #74 because the archive step depends on the legacy daemon CLI command removal in that branch.

Verification

• cargo fmt --manifest-path rust/Cargo.toml -- --check
• bash scripts/ci/run-fast-checks.sh
• git diff --check
• cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
• cargo test --manifest-path rust/Cargo.toml --test native_app_e2e
• cargo test --manifest-path rust/Cargo.toml --test security_regressions
• cargo test --manifest-path rust/Cargo.toml --all-targets
• rg -n "\\b(apw host|legacy_parity|browser-bridge/|native-host/|install-browser-bridge|build-native-host|browser-host-smoke|RuntimeMode::(Direct|Launchd|Browser|Native)|\\\"launchd\\\")\\b" .github docs rust/src rust/tests scripts -S

Notes

• This PR should merge after Remove legacy daemon CLI commands #74.
• The legacy source is preserved under legacy/ for historical audit work; it is no longer part of active CI or the supported runtime surface.