feat(ParseConfig): Add record + Parse(config) overload (additive)

[dimension-zero]

feat(ParseConfig): Add record + Parse(config) overload (additive)

• ArgumentParser.fs: Introduce public ParseConfig record carrying
  Inputs, ConfigurationReader, IgnoreMissing, IgnoreUnrecognized,
  RaiseOnUsage. Provide ParseConfig.Default reproducing the historical
  Parse(...) defaults.
• New Parse(config: ParseConfig) overload delegates to the existing
  Parse(?inputs, ?configurationReader, ...) implementation. All current
  overloads remain untouched, so existing callers see no shape change.

Useful when hosts want to layer configuration programmatically (e.g.
merging container-provided defaults with user overrides) rather than
juggling many optional method arguments.

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test(ParseConfig): Add coverage for ParseConfig record + Parse(config)

6 new tests:

• ParseConfig.Default holds the historical defaults (None inputs, None
  reader, false IgnoreMissing/IgnoreUnrecognized, true RaiseOnUsage).
• Parse(config with explicit inputs) parses those inputs.
• Parse(config) matches Parse(?inputs, ...) for the same shape.
• IgnoreMissing=true skips the mandatory check on empty inputs.
• IgnoreUnrecognized=true gathers unknown args into UnrecognizedCliParams.
• ConfigurationReader provided via config sources AppSettings entries.

A separate non-mandatory schema is used for the AppSettings test because
Argu's missing-mandatory check fires from CLI parsing even when AppSettings
provides a value (existing behaviour, not introduced by PR 19).

Net suite size on this branch: 112 -> 118.

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