[akeit0]

Recreates #384 as an opt-in platform policy, preserving the existing managed default.

public enum LuaNumberFormat
{
    DotNet,
    Lua
}

using var state = LuaState.Create(LuaPlatform.Default with
{
    NumberFormat = LuaNumberFormat.Lua
});

DotNet preserves invariant managed numeric text. Lua uses Lua 5.2's default C-locale %.14g: 14 significant digits, lowercase exponents, signed zero, and portable signed inf/nan. For example, tostring(1/3) produces 0.33333333333333.

The option covers tostring and numeric __tostring results, %s/%q, concatenation, table.concat, all numeric gsub replacements, explicit-base tonumber numeric inputs, and numeric I/O (including accepted numeric input/output filenames). Coroutines inherit it independently of string mode. Explicit floating-point formats retain their requested finite precision; their special-value spellings follow the option. Public C# LuaValue.ToString(), arithmetic, NaN bits and parsing of numeric strings remain unchanged.

C Lua 5.2 details

• luaconf.h defines the default LUA_NUMBER_FMT as %.14g. Numeric coercion and numeric I/O use it.
• Explicit string formats call C sprintf; they do not all use 14 digits. %q quotes numeric text in Lua 5.2.
• Special-value spelling is CRT-dependent. Windows can emit nan(ind)/nan(snan), as Microsoft documents. The Lua option normalizes these to signed nan, without serializing CRT classifier suffixes or changing the input bits. Existing portable finite %a formatting is retained; Windows CRT hexadecimal-format quirks are not emulated.
• Fourteen-digit output can lose round-trip precision. tonumber(1e14,10) returns nil in Lua mode because its intermediate text is 1e+14; the managed default is preserved.

Validation

• Release solution build: all four runtime targets, zero warnings/errors.
• Full runtime suites pass on .NET 8 and .NET 10; all 73 generator tests pass.
• All 58 policy cases pass on each framework, covering both policies, culture, rounding boundaries, subnormals, signed quiet/signaling NaNs, explicit formats, I/O in both string modes, numeric filenames and coroutine inheritance.
• Native C Lua 5.2 comparison: 18,567 implicit conversions and 15 I/O cases, with zero differences after normalizing Windows NaN suffixes. Another 2,700 explicit-format comparisons identify the existing CRT-specific hexadecimal spelling/flag differences described above.
• CSharpier and benchmark --verify pass.
• Paired .NET 10 conversion benchmarks keep the managed default within about 4% of main, with unchanged allocations. The sampled Lua-mode conversions of 1/3 are about 4–16% faster with their shorter output; this is workload-specific.