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

[unarbos]

Summary

• add governance proposal listing support via agcli admin raw --call proposals --args '[]'
• implement chain query support for proposal discovery with governance-pallet fallback (Triumvirate then Senate), including vote/call-data snapshots when available
• add an e2e-gated localnet smoke test for list_senate_proposals
• update docs/commands/admin.md and flip matrix row btcli.sudo.proposals to COVERED_E2E

Verification

• SKIP_METADATA_FETCH=1 cargo build --release --bin agcli
• SKIP_METADATA_FETCH=1 cargo test --features e2e senate_proposals_query_localnet_smoke -- --nocapture
• target/release/agcli localnet start --output json && target/release/agcli --network local --output json admin raw --call proposals --args '[]' && target/release/agcli localnet stop

Notes

• localnet image does not currently expose a governance proposals pallet with active entries in default state, so the CLI returns {"count":0,"proposals":[]} on fresh localnet while still validating read-path behavior end-to-end.