feat: add native compiled pattern state API

[jbachorik]

Summary

Adds a deliberately narrow native compiled-pattern API for the named linear-token-sequence profile:

• immutable request/result/pattern types with only NONE and DOTALL native-profile flags;
• a per-input, single-thread-confined match state that retains spans but never the input;
• whole-match and named-group absolute span access without creating a String, subsequence, MatchResult, fallback matcher, or compiler-cache entry.

The API invokes only the L1e direct native-admission path. Rejection remains explicit and never falls through to the general compiler or JDK fallback.

Validation

• ./gradlew :reggie-runtime:test --tests com.datadoghq.reggie.runtime.ReggieCompiledPatternTest --tests com.datadoghq.reggie.runtime.NamedOnlyLtsAdmissionTest
• ./gradlew :reggie-runtime:test
• ./gradlew spotlessApply
• ./gradlew jacocoVerify build
• final implementation-plan validation: clean
• final independent code review: clean

[Copilot]

Pull request overview

Adds a new intentionally narrow “native compiled pattern” API for the named linear-token-sequence (LTS) profile in reggie-runtime, enabling span extraction without materializing inputs or touching the general compiler/cache paths.

Changes:

• Introduces new public native-compilation API types (ReggieCompiledPattern, request/flag/result/rejection types) that only use the direct named-only LTS admission path.
• Adds ReggieMatchState to hold per-input, single-thread-confined match state that stores only absolute spans (no retained input).
• Extends LinearTokenSequenceMatcher with workspace reuse and named-group index helpers, plus tests validating cache non-mutation, span behavior, and parallel state usage.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/ReggieCompiledPatternTest.java	Adds coverage for new native compiled-pattern API behavior (admission/rejection, spans, cache invariants, parallel state).
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieMatchState.java	Implements single-thread-confined match state that stores spans only and exposes group span APIs.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompileRequest.java	Adds immutable request record for the native compilation profile.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompileFlag.java	Defines the restricted native-profile flags (NONE, DOTALL) and maps to ReggieFlags.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompiledPattern.java	Adds entry point for native compilation and state creation.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompilationResult.java	Adds admitted/rejected result wrapper for native compilation attempts.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompilationRejection.java	Adds public rejection reasons for native compilation.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/LinearTokenSequenceMatcher.java	Exposes workspace reuse + group helpers needed by ReggieMatchState.
reggie-runtime/src/main/java/com/datadoghq/reggie/ReggieFlags.java	Adds ReggieFlags.NONE constant.

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