fix(tracing): Set sentry.op to function in new trace decorator

[sentrivana]

Description

We weren't setting sentry.op in spans created with the @sentry_sdk.traces.trace decorator, so they'd show up with a fallback name in the product.

Issues

Closes #6795

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

[github-actions]

Codecov Results 📊

✅ 91020 passed | ⏭️ 6302 skipped | Total: 97322 | Pass Rate: 93.52% | Execution Time: 315m 54s

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2439 uncovered lines.
✅ Project coverage is 89.79%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/tracing_utils.py	100.00%	⚠️ 1 partials

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    89.76%    89.79%    +0.03%
==========================================
  Files          193       193         —
  Lines        23888     23891        +3
  Branches      8250      8252        +2
==========================================
+ Hits         21442     21452       +10
- Misses        2446      2439        -7
- Partials      1353      1354        +1

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Generated by Codecov Action

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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