feat(admin): close GAP btcli.sudo.senate

[unarbos]

Summary

• add Client::list_senate_members() in src/chain/queries.rs with governance pallet fallback (SenateMembers, Triumvirate, Senate) and robust missing-pallet/storage handling
• add agcli admin raw --call senate --args '[]' read-only alias in src/cli/admin_cmds.rs (plus alias variants) with JSON/text output for senate members
• add localnet smoke coverage chain::queries::tests::senate_members_query_localnet_smoke
• update admin command docs and flip parity matrix row btcli.sudo.senate to COVERED_E2E

Verification

• SKIP_METADATA_FETCH=1 cargo build --release --bin agcli
• cargo test --features e2e senate_list_aliases_are_recognized -- --nocapture
• cargo test --features e2e validate_empty_json_array_requires_no_args -- --nocapture
• cargo test --features e2e senate_members_query_localnet_smoke -- --nocapture
• cargo test --features e2e -- --nocapture (fails in existing unrelated test: events::tests::pretty_subtensor_variants_are_exhaustive)

Parity row

• btcli.sudo.senate: GAP -> COVERED_E2E