feat: add bounded native pattern cache

[jbachorik]

Summary

Adds an opt-in, bounded, instance-owned cache for native named-LTS compiled patterns.

• Successful native patterns are cached with exact LRU capacity.
• Rejections are never cached; legacy RuntimeCompiler caches remain untouched.
• Equal concurrent requests share in-flight admission; clear and exceptional admission behavior are deterministic and tested.

Validation

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

[Copilot]

Pull request overview

Adds an opt-in, bounded, instance-owned cache for native named linear-token-sequence (LTS) compiled patterns, including a configurable “maximum source length” budget gate and single-flight behavior for concurrent identical compile requests.

Changes:

• Introduces ReggieCompiledPatternCompiler with an exact-capacity LRU cache and in-flight deduplication using CompletableFuture.
• Adds ReggieNativeCompileBudget and a new rejection reason SOURCE_TOO_LONG for over-budget requests.
• Adds comprehensive unit tests covering LRU eviction/recency, cache independence, deterministic exceptional admissions, and budget boundary + concurrency behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompiledPatternCompiler.java	New bounded, instance-owned LRU cache + in-flight single-flight admission mechanism.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieNativeCompileBudget.java	New budget type for rejecting overly long sources prior to admission/in-flight registration.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompiledPattern.java	Refactors compilation entry to route through tryCompileNative helper used by the compiler.
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/ReggieCompilationRejection.java	Adds SOURCE_TOO_LONG rejection reason.
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/ReggieCompiledPatternCompilerTest.java	New tests for LRU behavior, independence, concurrency single-flight, clear-during-admission, and exceptional admissions.
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/ReggieNativeCompileBudgetTest.java	New tests for budget validation, UTF-16 length semantics, and concurrency behavior under budget rejection.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit:0bec80d15e

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.41758% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.4%. Comparing base (f7b758a) to head (9d259b3).

Files with missing lines	Patch %	Lines
.../reggie/runtime/ReggieCompiledPatternCompiler.java	86.8%	7 Missing and 3 partials ⚠️
...atadoghq/reggie/runtime/ReggieCompiledPattern.java	40.0%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@## agent/logs-reggie-l1g #118 +/- ##
=========================================================
- Coverage 84.4% 84.4% -0.1% 
Complexity 1 1 =========================================================
Files 153 155 +2 Lines 43194 43283 +89 Branches 5898 5910 +12 =========================================================
+ Hits 36498 36571 +73 - Misses 4906 4918 +12 - Partials 1790 1794 +4 

Files with missing lines	Coverage Δ
...ghq/reggie/runtime/ReggieCompilationRejection.java	100.0% <100.0%> (ø)
...oghq/reggie/runtime/ReggieNativeCompileBudget.java	100.0% <100.0%> (ø)
...atadoghq/reggie/runtime/ReggieCompiledPattern.java	70.0% <40.0%> (-30.0%)	⬇️
.../reggie/runtime/ReggieCompiledPatternCompiler.java	86.8% <86.8%> (ø)

---

Continue to review full report in Codecov by Harness.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f7b758a...9d259b3. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.