feat(ffe): add native evaluation bridge

[leoromanovsky]

Motivation

This is PR H in the PHP OpenFeature compatibility stack. It starts the tracer native runtime path by importing libdatadog/datadog-ffe into dd-trace-php and exposing a small bridge for the PHP feature flag client.

Shared planning/reference doc: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0

Stack context: this PR is stacked on #3902. The native bridge shape follows the DDTrace\ffe_* approach from #3630 while keeping Remote Config lifecycle and exposure delivery in later stack slices.

Changes

• Adds datadog-ffe as a direct components-rs dependency and registers components-rs/ffe.rs.
• Adds a Rust bridge that stores UFC config, evaluates through datadog_ffe::rules_based, and maps value/reason/error fields into a C/PHP result object.
• Exposes internal DDTrace\ffe_evaluate, DDTrace\ffe_has_config, DDTrace\ffe_config_version, and DDTrace\ffe_load_config functions.
• Adds DDTrace\FeatureFlags\NativeEvaluator and makes Client::create() prefer it when the extension bridge is available.
• Keeps the transitional user warning/provider state when the native bridge exists before Remote Config and exposure delivery are complete.
• Adds native bridge PHPT coverage and CODEOWNERS entries for the Rust bridge and extension tests.

Decisions

• Import libdatadog/datadog-ffe; do not reimplement the evaluator locally in PHP or C.
• Keep this PR limited to the minimal evaluation bridge. Remote Config lifecycle wiring remains PR I.
• Keep native exposure flush/dedup/fork/ZTS integration out of this slice; that remains PR J.
• Keep OpenFeature SDK dependencies out of the root tracer package so PHP 7 installability remains intact.

Verification

• php -n -l src/api/FeatureFlags/NativeEvaluator.php
• php -n -l src/api/FeatureFlags/Client.php
• php -n -l tests/ext/ffe/native_bridge_evaluate.phpt
• git diff --check
• RUSTC_BOOTSTRAP=1 cargo check -p ddtrace-php
• EXTRA_CFLAGS="-I$(brew --prefix pcre2)/include" EXTRA_LDFLAGS="-L$(brew --prefix pcre2)/lib" make -j"$(sysctl -n hw.ncpu)"
• php -n -d extension=tmp/build_extension/modules/ddtrace.so -m | rg -i "^ddtrace$"
• make test_c TESTS=tests/ext/ffe/native_bridge_evaluate.phpt
• Direct client smoke with built ddtrace.so confirming fallback value, PROVIDER_NOT_READY, native transitional warning, and provider state when no FFE config is loaded.

[datadog-datadog-prod-us1]

 

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 14 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.0]     

🔧 Fix in code (Fix with Cursor).

1 failed test. Assertion Error: Expected 'Datadog-backed PHP feature flag evaluation is not fully enabled yet. Returning default values until the ddtrace FFE runtime path is available.', got 'Datadog-backed PHP feature flag evaluation is using the native bridge before Remote Config and exposure delivery are fully enabled.' at /go/src/github.com/DataDog/apm-reliability/dd-trace-php/tests/api/Unit/FeatureFlags/ClientTest.php:107

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.1]     

🔧 Fix in code (Fix with Cursor).

1 failed test. Error: Failed asserting that two strings are identical in ClientTest.php:107.

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.2]     

🔧 Fix in code (Fix with Cursor).

1 failed test. Assertion Error: Expected feature flag evaluation message was not returned: expected 'Datadog-backed PHP feature flag evaluation is not fully enabled yet...' but got 'Datadog-backed PHP feature flag evaluation is using the native bridge...'.

View all 14 failed jobs.

ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 60.70% (+0.00%)

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[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-05-22 00:19:11

Comparing candidate commit d712d6b in PR branch leo.romanovsky/pr-h-native-bridge with baseline commit 24d062a in branch leo.romanovsky/pr-e-exposure-metrics.

Found 0 performance improvements and 4 performance regressions! Performance is the same for 190 metrics, 0 unstable metrics.

scenario:SamplingRuleMatchingBench/benchRegexMatching1

• 🟥 execution_time [+86.835ns; +153.965ns] or [+6.070%; +10.763%]

scenario:SamplingRuleMatchingBench/benchRegexMatching2

• 🟥 execution_time [+39.214ns; +86.386ns] or [+2.649%; +5.836%]

scenario:SamplingRuleMatchingBench/benchRegexMatching3

• 🟥 execution_time [+45.874ns; +119.726ns] or [+3.138%; +8.189%]

scenario:TraceAnnotationsBench/benchTraceAnnotationOverhead-opcache

• 🟥 execution_time [+3.652µs; +8.364µs] or [+2.057%; +4.710%]