chore: add span percentile in trace details

[nityanandagohain]

Fixes https://github.com/SigNoz/engineering-pod/issues/3264

Adds details about span percentile.

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Project	Deployment	Review	Updated (UTC)
signoz-web	Ready	Preview, Comment	Dec 26, 2025 6:16pm

[claude]

Claude finished @nityanandagohain's task in 1m 33s —— View job

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Documentation Review

Tasks

• Read CONTRIBUTING.md guidelines
• Review span-details.mdx changes
• Verify technical accuracy
• Check image references
• Post review feedback

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Summary

This PR successfully adds documentation for the span percentile feature in the trace details page. The changes are well-structured and follow most documentation guidelines. I've identified a few minor issues for improvement.

Issues Found

Minor Issues:

1. Line 80 - Phrasing: "over the last one hour" → "over the past hour" (more natural English)
2. Line 98 - Missing period at the end of the sentence before the figure tag

PR Checklist Compliance

Reviewing against the PR Checklist:

• ✅ Frontmatter: Complete with date (updated to 2025-12-26), id, title, and description added
• ✅ Images: Three new PNG images properly placed in /public/img/docs/apm-and-distributed-tracing/ and referenced correctly
• ✅ Content accuracy: The span percentile concept is technically sound and aligns with OpenTelemetry distributed tracing principles for performance analysis
• ✅ Structure: Properly uses H4 headings (####) for subsections under "Detailed Span Inspection"
• ✅ Figure components: Correctly uses <figure> with data-zoomable, proper alt attributes, and captions

Note on image format: The images are in PNG format. Per CONTRIBUTING.md guidelines (line 267), WebP format (.webp) is preferred for all images. Consider converting these images to WebP format for better performance. See the Creating WebP images guide.

Technical Accuracy

The span percentile documentation is technically accurate. The feature description aligns with standard OpenTelemetry span performance analysis practices, where percentiles (p50, p90, p95, p99) are commonly used to identify performance outliers and understand latency distributions across distributed traces.

Sources:

• Understanding OpenTelemetry Spans in Detail | SigNoz
• Span Metrics - Nais

Recommendation

This documentation is ready to merge after addressing the two minor inline comments. The content effectively explains the new span percentile feature and provides clear visual examples for users.