fix(topograph): tune topology request latency buckets for better percentile accuracy

[dmitsh]

No description provided.

[greptile-apps]

Greptile Overview

Greptile Summary

This PR replaces Prometheus default buckets (0.005 to 10 seconds) with custom buckets (1 to 30 seconds) for the topograph_request_duration_seconds histogram. The new buckets are better suited for topology request latencies which typically take several seconds to complete.

• Changed histogram buckets from prometheus.DefBuckets to custom range [1, 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 25, 30] seconds
• Improves percentile accuracy (p50, p90, p95, p99) for topology requests which are inherently slower than HTTP requests
• HTTP request metrics still use default buckets, which is appropriate for faster operations

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change is a simple, well-scoped metrics configuration update that replaces default Prometheus histogram buckets with domain-specific buckets. The new buckets (1-30 seconds) align with the expected latency range for topology requests, improving observability without affecting functionality.
• No files require special attention

Important Files Changed

Filename	Overview
pkg/metrics/metrics.go	Replaced default Prometheus buckets with custom buckets (1-30 seconds) tailored for topology request latencies

_{Last reviewed commit: f318ae1}

[greptile-apps]

_{1 file reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.94%. Comparing base (89c4290) to head (f318ae1).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #215   +/-   ##
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  Coverage   65.94%   65.94%           
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  Files          82       82           
  Lines        4493     4493           
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  Hits         2963     2963           
  Misses       1418     1418           
  Partials      112      112           

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[ravisoundar]

lgtm