feat: refine CLI command and help UX

[Icemap]

Summary

• Remove the console-style --confirm-file-system-name requirement from tdc fs delete-file-system.
• Make bare tdc return an AWS-style two-level usage error while preserving explicit help and version paths.
• Format help flag types as <type>, mark required flags with (required), and label the configure value as Default region code.
• Start human-readable error output with a blank line for clearer terminal separation.
• Update tests, README, AGENTS, completed specs, CI cleanup, and documentation; remove the unused docs-cn submodule.

Why

The CLI should be predictable for both terminal users and agents. Filesystem deletion no longer repeats the resource name as a console confirmation, root invocation has a deterministic usage result, and generated help now distinguishes required inputs from optional inputs without requiring users to infer the command contract.

User impact

• Filesystem deletion requires only --file-system-name.
• Bare tdc writes a compact synopsis to stderr and exits with code 2; tdc help remains successful.
• Flags and Global Flags render typed values such as <string>, and required flags are marked explicitly.
• Configure help and prompts describe Default region code.
• Human-readable errors begin on a new line.

Validation

• make test
• make e2e
• direct bin/tdc help, stderr byte, and exit-code verification
• git diff --check