feat: add interruptible native matching

[jbachorik]

Summary

Adds opt-in cooperative interruption for the native named LTS API.

• InterruptibleCharSequence supplies a caller-thread cancellation/deadline hook.
• Plain CharSequence keeps the existing context-free matching path.
• Interruptible inputs receive bounded charAt() checkpoints, with exception identity preserved and match state cleared on cancellation.

Validation

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

[Copilot]

Pull request overview

This PR adds an opt-in cooperative interruption mechanism for Reggie’s native LinearTokenSequence-based matching, allowing callers to supply a cancellation/deadline hook via an InterruptibleCharSequence while preserving existing behavior for plain CharSequence inputs.

Changes:

• Introduces InterruptibleCharSequence as a CharSequence with a synchronous checkInterrupted() callback.
• Adds an interruptible execution path in ReggieMatchState and LinearTokenSequenceMatcher using a checkpointing wrapper (bounded to every 256 charAt() calls).
• Adds targeted runtime tests validating checkpoint frequency, exception identity propagation, and match-state clearing on cancellation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/InterruptibleCharSequenceTest.java	Adds coverage for interruptible matching behavior, checkpoint bounds, and state clearing semantics.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieMatchState.java	Routes interruptible inputs to a new interruptible matcher path and tracks which path was used.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/LinearTokenSequenceMatcher.java	Implements checkpointing via a CharSequence wrapper and an interruptible match entrypoint.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/InterruptibleCharSequence.java	Defines the interruptible input contract and documents usage constraints.

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Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (agent/logs-reggie-l1f@561a013). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...ghq/reggie/runtime/LinearTokenSequenceMatcher.java	85.7%	2 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## agent/logs-reggie-l1f #117 +/- ##
=======================================================
Coverage ? 84.4% Complexity ? 1 =======================================================
Files ? 153 Lines ? 43194 Branches ? 5898 =======================================================
Hits ? 36498 Misses ? 4906 Partials ? 1790 

Files with missing lines	Coverage Δ
...atadoghq/reggie/runtime/ReggieCompiledPattern.java	100.0% <100.0%> (ø)
...com/datadoghq/reggie/runtime/ReggieMatchState.java	100.0% <100.0%> (ø)
...ghq/reggie/runtime/LinearTokenSequenceMatcher.java	81.3% <85.7%> (ø)

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