feat: make policy length limits configurable per engine (#624)

- Add PolicyLengthConfig struct with max_col, max_file_bytes, and
  max_lines fields, replacing hardcoded constants in the lexer.
- Add Engine::set_policy_length_config and clear_policy_length_config
  to allow callers to override the default limits.
- Add Source::from_contents_with_limits and from_file_with_limits for
  direct Source construction with custom limits; existing from_contents
  and from_file signatures are preserved using defaults.
- Add tests for default rejection, custom limits, and engine plumbing.
- Add bindings for C, C++, Python, WASM/JS, Java, Ruby, C#, Go

bindings/ruby/ext/regorusrb/Cargo.toml

@@ -18,5 +18,6 @@ coverage = ["regorus/coverage"]
 [dependencies]
 magnus = { version = "0.8.2" }
 regorus = { path = "../../../..", default-features = false, features = ["arc"] }
+serde = { version = "1", features = ["derive"] }
 serde_json = "1.0.140"
 serde_magnus = "0.11.0"