fix(cdk-cli): parse --unit consistently and scope balance by currency

[b-l-u-e]

This PR improves how the global --unit flag is parsed and how balance uses it, so the CLI no longer misleads users about which currency unit they are acting on. Plural aliases and a typo check align input with Cashu’s standard units; --unit is global so it works both before and after the subcommand.

issues i faced

Ambiguous or misleading unit handling

A typo or odd string could still parse as a custom unit, so what i typed did not match what i saw on the screen. For example, a mistyped unit could still show sat balances as if nothing was wrong:

cdk --unit satt balance
 http://127.0.0.1:8085 100 sat

Total balance across all wallets: 179 sat

balance and --unit

--unit did not line up with what i expected for balance. Asking for non-matching unit could still show sat totals. And putting --unit after the subcommand failed entirely:

cdk --unit dollarz balance
 http://127.0.0.1:8085 100 sat

Total balance across all wallets: 179 sat

cdk balance --unit usd
error: unexpected argument '--unit' found

Usage: cdk-cli balance

For more information, try '--help'.

Whereas putting --unit before the command still did not filter to that unit when you only held sat:

cdk --unit usd balance
0: http://127.0.0.1:8085 100 sat
1: https://fake.thesimplekid.dev 79 sat

Total balance across all wallets: 179 sat

Empty --unit

Passing an empty value looked like “no unit,” but the tool still behaved like a normal sat run, which is not the same as omitting --unit on purpose:

cdk --unit "" balance
0: http://127.0.0.1:8085 100 sat

Total balance across all wallets: 179 sat

What this PR changes

• Stricter parsing: plural aliases, explicit error for satt, clear error for empty --unit (omit the flag for default sat).
• balance respects the resolved unit (default sat when --unit is omitted).
• global = true on --unit so cdk balance --unit usd and cdk --unit usd balance are equivalent.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.55%. Comparing base (87f5c7c) to head (609da8b).
⚠️ Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1876      +/-   ##
==========================================
- Coverage   63.59%   63.55%   -0.05%     
==========================================
  Files         329      329              
  Lines       54881    54881              
==========================================
- Hits        34904    34878      -26     
- Misses      19977    20003      +26     

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[lescuer97]

logic change

[lescuer97]

I think you want this to be and Option and filter if it's not None

[thesimplekid]

Close for #1930