feat(hypecli): add HIP-4 outcome commands

[ifdario]

Adds a new hypecli outcome command group for HIP-4 outcome tokens:

• outcome list [--chain]: prints outcomes (ID, name, sides, description) and questions (ID, name, outcome IDs, settled IDs, fallback) from the outcomeMeta info endpoint, so users can discover the integer IDs the write commands need.
• outcome split --outcome --amount: split the quote token into one share of each side.
• outcome merge --outcome [--amount]: merge matching shares back into the quote token; omitting --amount merges the maximum available.
• outcome merge-question --question [--amount]: merge a full set of mutually-exclusive outcomes within a question.
• outcome negate --question --outcome --amount: convert shares of one outcome into the complementary basket.

Write commands reuse the shared SignerArgs and follow the vault.rs pattern (find_signer_sync + HttpClient + NonceHandler), passing None for vault_address/expires_after like the other write commands. Since userOutcome is an L1 agent-signed action, agent (API wallet) keys work out of the box; this is now documented in --agent-help and the --private-key flag help.

Verified: clean build, no new clippy warnings, help output for all subcommands, and outcome list against live mainnet and testnet. Write paths are thin wrappers over the SDK methods exercised by examples/hypercore/split_merge_outcome.rs; not yet exercised with a funded key from the CLI.