chore(cli)!: rename --chain-id to --chain

[dhfang]

For consistency - we use chain or chain-a or counterparty-chain in more places than chain-id.

[greptile-apps]

Greptile Summary

The PR consistently renames the chain-selection flag from --chain-id to --chain for configuration and relayer commands.

• Introduces a shared flagChain constant.
• Updates flag registration and required-flag metadata together.
• Reuses the constant for commands that already exposed --chain.

Confidence Score: 5/5

The PR appears safe to merge; the intentional breaking flag rename is applied consistently and has no affected in-repository consumers.

Flag declarations and required-flag markers use the same new name, while the affected commands neither inherit conflicting flags nor have repository callers using the removed spelling.

Important Files Changed

Filename	Overview
link/cmd/ibc/main.go	Consistently applies the intentional CLI flag rename without introducing registration mismatches or command-hierarchy collisions.

_{Reviews (1): Last reviewed commit: "refactor(cli)!: rename --chain-id to --c..." | Re-trigger Greptile}