Add Regex.Escape via cre2_quote_meta

[Copilot]

IronRe2 lacked a way to escape regex metacharacters for literal matching — useful when building patterns programmatically or integrating with RE2-based systems (e.g. Prometheus).

Changes

• Re2Ffi.cs — P/Invoke binding for cre2_quote_meta, which delegates to RE2::QuoteMeta
• Regex.cs — Two static Regex.Escape overloads: string and ReadOnlySpan<byte>. The native function heap-allocates the result via malloc; freed with NativeMemory.Free for cross-platform correctness
• RegexTests.cs — Tests for metacharacter escaping, plain strings, empty input, and a round-trip literal match

Usage

var escaped = Regex.Escape("1+1=2 (really!)");
// => "1\+1\=2 \(really\!\)"

using var re = new Regex(escaped);
re.IsMatch("1+1=2 (really!)"); // true
re.IsMatch("1+1=2 Xreally!Y"); // false

[Copilot]

Pull request overview

Adds an Escape API to IronRe2’s Regex class (backed by RE2’s “quote meta” functionality via cre2_quote_meta) so callers can safely turn literal text/bytes into a regex pattern that matches literally.

Changes:

• Added cre2_quote_meta P/Invoke declaration in Re2Ffi.
• Added Regex.Escape(string) and Regex.Escape(ReadOnlySpan<byte>) implementations.
• Added xUnit tests covering basic escaping and a literal-match smoke test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/IronRe2/Re2Ffi.cs	Adds native interop signature for cre2_quote_meta.
src/IronRe2/Regex.cs	Adds public Escape APIs and unmanaged interop/cleanup logic.
test/IronRe2.Tests/RegexTests.cs	Adds test coverage for the new Regex.Escape APIs.

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[corpo-iwillspeak]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Done in bde98bf:

• Added an if (input.IsEmpty) return string.Empty; fast-path at the top of Escape(ReadOnlySpan<byte>) to avoid passing a null pointer to native code when the span is empty.
• Extended EscapeData with additional cases covering \\ (backslash), {} (braces), ?, |, and \n (newline — RE2 escapes it as \ + literal newline).