manager: return an error for truncated adaptor signature lists

[bennyhodl]

Summary

Fixes the Bitcoin Red Team finding FND-006, "Truncated adaptor-signature lists in counterparty messages panic the DLC message-handler task". The enum descriptor, the numeric trie (serial and parallel), and the CET settlement paths indexed the wire-supplied adaptor signature vector without a length check. An AcceptDlc or SignDlc with a short list panicked inside on_dlc_message; both transports awaited the handler inline and nothing restarted the listener, so one malformed accept from any peer silenced DLC message processing until the process restarted. The auditor's re-run reproduced the panic at enum_descriptor.rs:129 on current master.

Changes

• EnumDescriptor::verify_adaptor_info, both verify_helper variants in ddk-trie, get_signed_cet in contract_updater, and the settled channel close in channel_updater use bounds-checked access and return an invalid argument or invalid state error naming the missing index and the received count.
• The parallel trie helper no longer unwraps on an empty trie, and carries the same too_many_arguments allowance as the serial one so clippy --all-features passes for the crate.
• The nostr and lightning transports run each inbound message in its own tokio::spawn task and await the join handle. A handler panic is logged with the counterparty and the loop continues, so a parser bug can no longer take the listener down. The nostr reply path logs event build and send failures instead of unwrapping them.

Testing

• New truncated_counterparty_adaptor_signatures_are_rejected in the stateless suite: an accept with an empty adaptor signature list now yields InvalidAccept mentioning the missing signature, where it panicked before.
• Stateless suite (33), ddk-trie with and without parallel (42), and the regtest enum_single_oracle_test and single_oracle_numerical_test pass. cargo check --all-features --tests and cargo +1.89.0 clippy -- -D warnings (the CI configuration) are clean.
• clippy --all-features still reports four pre-existing lints in ddk/src/oracle/nostr.rs and p2p_derivatives.rs that are untouched here and not part of the CI gate.