refactor: remove ensureSampled, use natural OTel root spans

[ankurs]

Summary

• Remove ensureSampled hack that injected a fake remote sampled span context to force ParentBased samplers to always sample worker spans
• The Tracing() middleware now lets NewInternalSpan create a natural OTel root span per tick, with sampling governed by the global TracerProvider's sampler
• Remove associated tests (TestEnsureSampled*) and unused imports

Test plan

• make test passes (all tests green with -race)
• make lint clean (golangci-lint + govulncheck)

Summary by CodeRabbit

• Refactor
  • Simplified tracing middleware by removing forced trace sampling logic for worker spans.
  • Removed obsolete trace sampling unit tests.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 572bd09a-b3d3-4891-9f2f-41aafa400c65

📥 Commits

Reviewing files that changed from the base of the PR and between 715239e and 91227d5.

📒 Files selected for processing (2)

• middleware/README.md
• middleware/tracing.go

📝 Walkthrough

Walkthrough

The tracing middleware is simplified by removing the ensureSampled helper function and associated sampling logic. Worker span sampling decisions are now delegated entirely to the global OpenTelemetry TracerProvider sampler, and the middleware no longer modifies the context before span creation.

Changes

Cohort / File(s)	Summary
Tracing Middleware Simplification middleware/tracing.go, middleware/tracing_test.go	Removes ensureSampled helper and crypto/rand-based TraceID/SpanID generation/injection logic. Middleware now relies on OpenTelemetry TracerProvider sampler for sampling decisions. Corresponding unit tests for ensureSampled behavior are removed.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 The sampler now decides what's traced,
No forcing hands, just nature's taste,
Less code to wrangle, clean and light,
The telemetry flows just right! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and clearly describes the main change: removing the ensureSampled function and switching to natural OpenTelemetry root spans. This accurately summarizes the primary refactoring work across both modified files.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch remove-ensure-sampled

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@middleware/tracing.go`:
- Around line 12-14: Docstring for the exported Tracing() function was changed
to mention "natural OTel root spans / global sampler"; run the documentation
task to regenerate the public README so the published docs match the updated
docstring by running the project's doc generation (make doc which invokes
gomarkdoc), verify README.md updates reflect the new wording for Tracing(), and
commit the regenerated README.md alongside your change.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1b1a85f8-5062-40b1-88cd-7a0a3834ee68

📥 Commits

Reviewing files that changed from the base of the PR and between 3626332 and 715239e.

📒 Files selected for processing (2)

• middleware/tracing.go
• middleware/tracing_test.go

💤 Files with no reviewable changes (1)

• middleware/tracing_test.go

[Copilot]

Pull request overview

This PR removes the ensureSampled span-context injection so worker-cycle spans are created as “natural” spans (without a synthetic sampled remote parent), allowing sampling decisions to be governed by the configured global OpenTelemetry TracerProvider sampler.

Changes:

• Removed ensureSampled logic (and its crypto/rand usage) from the Tracing() middleware.
• Updated Tracing() documentation to reflect sampler-governed behavior.
• Removed TestEnsureSampled* tests and related unused imports.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
middleware/tracing.go	Stops forcing sampling via injected remote span context; relies on global OTel sampler and updates comments accordingly.
middleware/tracing_test.go	Removes tests and imports that only validated the deleted ensureSampled helper.

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