perf(stacktrace): defer shortFuncName to kept frames; drop Sprintf in frame.String

[samber]

Summary

• newStacktrace: compute shortFuncName only for frames that survive filtering — runtime/oops-internal frames (typically half the captured buffer) no longer pay the string slicing + Replacer allocation.
• frame.String: direct string concatenation with strconv.Itoa instead of two reflection-based fmt.Sprintf calls — runs once per frame on every stack trace formatting.
• getSourceFromFrame: builtin max/min instead of lo.Max/lo.Min, which allocated a []int per call.

Benchmarks

goos: darwin / goarch: arm64 / cpu: Apple M3, -count=10 -cpu=1

        │ before.txt  │             after.txt              │
        │   sec/op    │   sec/op     vs base               │
New       2.339µ ± 2%   2.202µ ± 4%  -5.84% (p=0.000 n=10)
Wrap      2.277µ ± 3%   2.122µ ± 3%  -6.79% (p=0.000 n=10)
geomean   2.307µ        2.162µ       -6.31%

        │  before.txt  │              after.txt              │
        │     B/op     │     B/op      vs base               │
New       2.352Ki ± 0%   2.336Ki ± 0%  -0.66% (p=0.000 n=10)
Wrap      2.336Ki ± 0%   2.320Ki ± 0%  -0.67% (p=0.000 n=10)
geomean   2.344Ki        2.328Ki       -0.67%

        │ before.txt │             after.txt              │
        │ allocs/op  │ allocs/op   vs base                │
New       15.00 ± 0%   13.00 ± 0%  -13.33% (p=0.000 n=10)
Wrap      14.00 ± 0%   12.00 ± 0%  -14.29% (p=0.000 n=10)
geomean   14.49        12.49       -13.81%

Test plan

• go build ./...
• go vet ./...
• go test ./...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.17%. Comparing base (ddcaa21) to head (052c234).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #136      +/-   ##
==========================================
- Coverage   90.18%   90.17%   -0.02%     
==========================================
  Files          15       15              
  Lines        1233     1231       -2     
==========================================
- Hits         1112     1110       -2     
  Misses         96       96              
  Partials       25       25              

Flag	Coverage Δ
unittests	90.17% <100.00%> (-0.02%)	⬇️

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[Copilot]

Pull request overview

This PR optimizes stacktrace capture and formatting in the oops package by reducing per-frame work (especially for filtered frames) and removing some allocation-heavy helpers in hot paths.

Changes:

• Defer shortFuncName computation until after frame filtering in newStacktrace.
• Replace fmt.Sprintf usage in oopsStacktraceFrame.String() with direct concatenation using strconv.Itoa.
• Replace lo.Max/lo.Min in source extraction with Go 1.21 builtin max/min.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
stacktrace.go	Reduces per-frame overhead in stack capture and speeds up frame string formatting.
sources.go	Eliminates lo usage for min/max bounds in source context extraction to avoid per-call allocations.

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