feat: add proxy compatibility diagnostics

[kev1n77]

Summary

• add a versioned compatibility diagnostic tree for Gateway and explicit Proxy capture
• track sanitized capture events per Proxy session and distinguish observed sessions from low-confidence proxy bypass or certificate-pinning hints
• surface actionable bundle, endpoint, CA, trust, recording, and session checks in Connection and Diagnostics
• include the request-free compatibility result in scanned support bundles
• keep CAP-007 partial because real process PID attribution remains outstanding

Verification

• cargo fmt --all -- --check
• cargo test --workspace --all-targets
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --manifest-path apps/desktop/src-tauri/Cargo.toml -- --check
• cargo test --manifest-path apps/desktop/src-tauri/Cargo.toml --all-targets
• cargo clippy --manifest-path apps/desktop/src-tauri/Cargo.toml --all-targets -- -D warnings
• npm run desktop:check (38 tests)
• npm run desktop:build
• browser QA at the default desktop viewport and 620x740; no dialog, diagnostic, or step overflow