feat(swap): add --chain flag for explicit chain selection (Vibe Kanban)

[MinaraAgent]

Summary

• Adds -c, --chain <chain> option to the swap command, allowing users to explicitly specify the blockchain
• Updates chain resolution logic to prefer the explicit --chain flag before falling back to token-derived chain
• Validates the --chain flag and warns the user if an unsupported chain is provided (instead of silently falling back)
• The transfer and withdraw commands already had this flag, so this brings swap to parity

Why

Previously, the swap command had no way to specify the chain explicitly. The chain was always derived from the resolved token, which could fail or be ambiguous when token lookup returned incomplete information. This made it impossible to disambiguate tokens that exist on multiple chains.

Implementation Details

• Added -c, --chain <chain> option to the swap command options
• Chain resolution now checks opts.chain first, normalizes it, and uses it if valid
• If user provides an invalid --chain value, we warn and exit instead of silently falling back
• Falls back to deriving chain from tokenInfo.chain if no explicit flag provided
• Shows a helpful error message if chain cannot be determined by either method
• Properly typed chain variable as Chain | undefined to match normalizeChain return type

Example Usage

minara swap -s buy -t ETH -a 20 --chain ethereum
minara swap -s sell -t BONK -a 1000 --chain solana

This PR was written using Vibe Kanban

[gemini-code-assist]

Code Review

This pull request introduces a --chain flag to the swap command, allowing users to explicitly specify the blockchain. The logic was updated to prioritize this flag over the chain derived from token information. Feedback indicates that the implementation is currently incomplete as it misses the same flag for transfer and withdraw commands mentioned in the PR description. Additionally, the chain resolution logic should be improved to validate user input and prevent silent fallbacks when an invalid chain is provided.