feat(langchain): Update LLM span operation to gen_ai.generate_text

[ericapisani]

Update LangChain integration to use the new gen_ai.generate_text operation for LLM call spans, aligning with OpenTelemetry semantic conventions.

Changes:

• Changed LLM span operation from gen_ai.pipeline to gen_ai.generate_text
• Updated span naming to include the model identifier: generate_text {model} instead of generic "Langchain LLM call"
• Removed unnecessary docstring from callback method
• Updated test assertions to validate the new operation and naming convention

This change improves observability by using more specific operation types that accurately reflect the semantic nature of LLM generation calls, and includes the model identifier for better span context.

Related to SDK-669. Replaces some of the changes introduced in #5705 (this is being broken down into 2 parts due to upcoming changes in the langchain test suite)

[linear-code]

SDK-669 Investigate use of `gen_ai.pipeline` span op across SDKs

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

---

New Features ✨

• (asgi) Add option to disable suppressing chained exceptions by alexander-alderman-webb in #5714

• (langchain) Update LLM span operation to gen_ai.generate_text by ericapisani in #5796

• (logging) Separate ignore lists for events/breadcrumbs and sentry logs by sl0thentr0py in #5698

Bug Fixes 🐛

Anthropic

• Set exception info on streaming span when applicable by alexander-alderman-webb in #5683
• Patch AsyncStream.close() and AsyncMessageStream.close() to finish spans by alexander-alderman-webb in #5675
• Patch Stream.close() and MessageStream.close() to finish spans by alexander-alderman-webb in #5674

Other

• (starlette) Catch Jinja2Templates ImportError by alexander-alderman-webb in #5741

Documentation 📚

• Add note on AI PRs to CONTRIBUTING.md by sentrivana in #5696

Internal Changes 🔧

• Pin GitHub Actions to full-length commit SHAs by joshuarli in #5781
• Add -latest alias for each integration test suite by sentrivana in #5706
• Use date-based branch names for toxgen PRs by sentrivana in #5704
• 🤖 Update test matrix with new releases (03/19) by github-actions in #5703
• Add client report tests for span streaming by sentrivana in #5677

Other

• Update CHANGELOG.md by sentrivana in #5685

---

_{🤖 This preview updates automatically when you update the PR.}

[github-actions]

Codecov Results 📊

✅ 13 passed | Total: 13 | Pass Rate: 100% | Execution Time: 7.04s

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 14381 uncovered lines.

Files with missing lines (1)

File	Patch %	Lines
langchain.py	3.28%	⚠️ 590 Missing

---

Generated by Codecov Action