fix: gate linear token sequences by flag profile

[jbachorik]

Summary

• admits named-capture Linear Token Sequences only for explicit Reggie DOTALL requests
• keeps source-inline modifiers and non-DOTALL semantic flags on the normal compiler route
• derives modifier status from original source before normalization, including escape, quote, class,
  and comment contexts
• converts logs LTS-positive fixtures to the Reggie-owned DOTALL API

Validation

• ./gradlew jacocoVerify build
• focused LTS, access-log, concurrency, and flag API suites
• final implementation-plan validation and independent code review

Stacked on #113 (which is stacked on #112 and #111).

[Copilot]

Pull request overview

This PR tightens when the runtime compiler may take the named-capture Linear Token Sequence (LTS) fast-path by requiring an explicit Reggie DOTALL flag profile (rather than source-inline modifiers), and adds tests to lock in the new routing behavior and cache interactions.

Changes:

• Gate LTS admission behind a source-derived “inline modifier present?” scan and an explicit Reggie DOTALL flag profile (not (?s) in the pattern text).
• Thread the LTS-admission profile through RuntimeCompiler.compile(...) into tryCompileLinearTokenSequence(...) / isRuntimeExecutableLinearTokenSequence(...).
• Update/add runtime tests to use the Reggie-owned DOTALL API and cover routing, cache-order independence, and inline-modifier detection.

Reviewed changes

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

File	Description
reggie-runtime/src/main/java/com/datadoghq/reggie/runtime/RuntimeCompiler.java	Introduces and propagates LinearTokenSequenceAdmission and adds a source scanner to block LTS when inline modifiers are present unless explicitly permitted by the Reggie DOTALL flag profile.
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/LinearTokenSequenceMatcherTest.java	Updates fixtures to use ReggieFlags.DOTALL and adds tests covering the new LTS gating rules and inline-modifier scanner behavior.
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/LinearTokenSequenceMatcherConcurrencyTest.java	Updates compilation of LTS fixtures to use explicit Reggie DOTALL when fixtures previously used a leading (?s).
reggie-runtime/src/test/java/com/datadoghq/reggie/runtime/LinearTokenSequenceAccessLogTest.java	Same fixture compilation update as concurrency test; centralizes it in a helper to convert leading (?s) into ReggieFlags.DOTALL.

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Codecov Report

❌ Patch coverage is 75.28090% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.4%. Comparing base (81f6dc5) to head (f4bb496).

Files with missing lines	Patch %	Lines
.../com/datadoghq/reggie/runtime/RuntimeCompiler.java	75.0%	6 Missing and 16 partials ⚠️

Additional details and impacted files

@@ Coverage Diff @@## agent/logs-reggie-l1c #114 +/- ##
=======================================================
Coverage 84.4% 84.4% Complexity 1 1 =======================================================
Files 147 147 Lines 42993 43067 +74 Branches 5860 5890 +30 =======================================================
+ Hits 36296 36367 +71 + Misses 4911 4905 -6 - Partials 1786 1795 +9 

Files with missing lines	Coverage Δ
...om/datadoghq/reggie/codegen/automaton/CharSet.java	90.2% <ø> (ø)
...ghq/reggie/runtime/LinearTokenSequenceMatcher.java	80.6% <100.0%> (ø)
.../com/datadoghq/reggie/runtime/RuntimeCompiler.java	87.0% <75.0%> (-1.0%)	⬇️

... and 4 files with indirect coverage changes

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