feat(langchain): Record reasoning token usage attribute

[alexander-alderman-webb]

Description

Record the reasoning token count from the provider-agnostic UsageMetadata dictionary.

Issues

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

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[github-actions]

Codecov Results 📊

✅ 99182 passed | ⏭️ 6527 skipped | Total: 105709 | Pass Rate: 93.83% | Execution Time: 346m 12s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -35
Passed Tests	📉 -83
Failed Tests	—
Skipped Tests	📈 +48

All tests are passing successfully.

✅ Patch coverage is 94.44%. Project has 2501 uncovered lines.
✅ Project coverage is 90%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/integrations/langchain.py	93.75%	⚠️ 1 Missing and 2 partials

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    89.99%    90.00%    +0.01%
==========================================
  Files          193       193         —
  Lines        24991     25008       +17
  Branches      9012      9038       +26
==========================================
+ Hits         22490     22507       +17
- Misses        2501      2501         —
- Partials      1437      1441        +4

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