feat(llmobs): add annotationContext API to annotate auto-generated spans

[sabrenner]

What does this PR do?

Adds an annotationContext, similar to our existing API in Python: https://docs.datadoghq.com/llm_observability/instrumentation/sdk?tab=python#annotating-auto-instrumented-spans.

Motivation

Allow users to annotate auto-instrumented spans within a certain scope/context - brings us more in-parity with the functionality of our Python SDK.

Additional Notes

The "context" part of the name annotationContext might not make as much sense in a Javascript/Node.js context versus Python, so I'm open to name changes before merging!

[github-actions]

Overall package size

Self size: 12.84 MB
Deduped: 115.54 MB
No deduping: 117.75 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | @datadog/libdatadog | 0.7.0 | 35.02 MB | 35.02 MB | | @datadog/native-appsec | 10.3.0 | 20.73 MB | 20.74 MB | | @datadog/native-iast-taint-tracking | 4.0.0 | 11.72 MB | 11.73 MB | | @datadog/pprof | 5.11.1 | 9.96 MB | 10.34 MB | | @opentelemetry/core | 1.30.1 | 908.66 kB | 7.16 MB | | protobufjs | 7.5.4 | 2.95 MB | 5.73 MB | | @datadog/wasm-js-rewriter | 4.0.1 | 2.85 MB | 3.58 MB | | @opentelemetry/resources | 1.9.1 | 306.54 kB | 1.74 MB | | @datadog/native-metrics | 3.1.1 | 1.02 MB | 1.43 MB | | @opentelemetry/api-logs | 0.206.0 | 201.39 kB | 1.42 MB | | @opentelemetry/api | 1.9.0 | 1.22 MB | 1.22 MB | | jsonpath-plus | 10.3.0 | 617.18 kB | 1.08 MB | | import-in-the-middle | 1.15.0 | 127.66 kB | 856.24 kB | | lru-cache | 10.4.3 | 804.3 kB | 804.3 kB | | @datadog/openfeature-node-server | 0.1.0-preview.10 | 95.11 kB | 401.46 kB | | opentracing | 0.14.7 | 194.81 kB | 194.81 kB | | source-map | 0.7.6 | 185.63 kB | 185.63 kB | | pprof-format | 2.2.1 | 163.06 kB | 163.06 kB | | @datadog/sketches-js | 2.1.1 | 109.9 kB | 109.9 kB | | lodash.sortby | 4.7.0 | 75.76 kB | 75.76 kB | | ignore | 7.0.5 | 63.38 kB | 63.38 kB | | istanbul-lib-coverage | 3.2.2 | 34.37 kB | 34.37 kB | | rfdc | 1.4.1 | 27.15 kB | 27.15 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB | | @isaacs/ttlcache | 1.4.1 | 25.2 kB | 25.2 kB | | tlhunter-sorted-set | 0.1.0 | 24.94 kB | 24.94 kB | | shell-quote | 1.8.3 | 23.74 kB | 23.74 kB | | limiter | 1.1.5 | 23.17 kB | 23.17 kB | | retry | 0.13.1 | 18.85 kB | 18.85 kB | | semifies | 1.0.0 | 15.84 kB | 15.84 kB | | jest-docblock | 29.7.0 | 8.99 kB | 12.76 kB | | crypto-randomuuid | 1.0.0 | 11.18 kB | 11.18 kB | | ttl-set | 1.0.0 | 4.61 kB | 9.69 kB | | mutexify | 1.4.0 | 5.71 kB | 8.74 kB | | path-to-regexp | 0.1.12 | 6.6 kB | 6.6 kB | | module-details-from-path | 1.0.4 | 3.96 kB | 3.96 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.14%. Comparing base (68ceae3) to head (cb217b6).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6571      +/-   ##
==========================================
+ Coverage   84.12%   84.14%   +0.02%     
==========================================
  Files         505      505              
  Lines       21027    21035       +8     
==========================================
+ Hits        17689    17700      +11     
+ Misses       3338     3335       -3     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-21 13:24:13

Comparing candidate commit cb217b6 in PR branch sabrenner/llmobs-annotation-context with baseline commit 68ceae3 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1598 metrics, 72 unstable metrics.

[Yun-Kim]

Logic lgtm, I am happy with whatever name you choose for annotationContext that might make more sense for javascript users!

[tlhunter]

[STDERR] Run benchmarks  | --2025-10-20 15:19:00--  (try: 3)  https://github.com/DataDog/sirun/releases/download/v0.1.10/sirun-v0.1.10-x86_64-unknown-linux-musl.tar.gz
[STDERR] Run benchmarks  | Connecting to github.com (github.com)|140.82.112.4|:443... failed: Connection timed out.

These failures may be related to today's AWS outage. I was able to manually download the tarball locally though. I'm kicking off another run.