keep-agent: hardening & test-coverage backlog (2 items)

[kwsantiago]

Backlog of hardening / test-coverage findings in keep-agent, verified still-open against current code by an automated triage pass. Each is an independent, pickup-able task — pick one and open a PR.

Findings

• Duplicate default_relay_opts across crates — Still duplicated across crates: keep-agent/src/client.rs:621 relay_opts() and keep-frost-net/src/node/mod.rs:2841 default_relay_opts() build the same RelayOptions, with no shared helper in keep-core.
• send_request returns on first decryptable event even if JSON parsing fails — keep-agent/src/client.rs:520-527 still returns Ok(decrypted) when request_id is Some and serde_json::from_str fails (the id-match check is skipped on parse error), so malformed JSON is returned as valid.

Grouped from individual tracked items; close each checkbox as its PR merges.