[KennyMcSimpson]

Plural formatting with Uzbek (uz) or Kyrgyz (ky) currently throws because neither language has a registered rule. Register both with DualOneOther, matching the CLDR cardinal rule n = 1 for one and other for other nonnegative values. This also supports regional and script-specific cultures through the existing language lookup.

The regression tests cover uz, uz-Latn-UZ, uz-Cyrl-UZ, ky, and ky-KG, integer/fractional values, and both a culture provider and explicit formatter options. All five regression cases fail before registration and pass afterward.

Validation:

• Complete tests using NUnitLite 4.3.0 with explicit en-US current/UI culture: 1,037 passed on .NET 6; 1,032 passed for the net462 target on .NET Framework.
• The default VSTest run on this Chinese UI environment has two existing culture-dependent failures; unchanged main reproduces the same two failures on both targets.
• Release build for all five library targets and NuGet package generation pass with no build warnings or errors. git diff --check passes.

Rules checked against CLDR 48 plurals.xml. Prepared with AI assistance and independently reviewed.

Closes #521.