Improve queue performance with optimized slice operations

[Copilot]

Performance improvements targeting slice allocation patterns and memory efficiency in queue operations.

Changes

• Slice insertion in AddJob: Replace double-append pattern with copy-based insertion

  // Before: O(n) extra allocation
  q.jobs = append(q.jobs[:idx], append([]Job{*job}, q.jobs[idx:]...)...)
  
  // After: In-place shift
  q.jobs = append(q.jobs, Job{})
  copy(q.jobs[idx+1:], q.jobs[idx:])
  q.jobs[idx] = *job

• Pre-allocate slices in Run() and Retry() with estimated capacity instead of growing dynamically

• Reuse slice capacity when clearing: execJobs = execJobs[:0] vs execJobs = []*Job{}

• Remove unnecessary allocation: Don't initialize Stacktrace to empty slice; nil is idiomatic

• Add benchmarks for key operations

Benchmark Results

Operation	Before	After	Improvement
Slice insertion	7.1μs, 40KB, 2 allocs	5.7μs, 32KB, 1 alloc	20% faster
Preallocated slice	5.4μs, 108 allocs	4.8μs, 100 allocs	11% faster

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• vuln.go.dev
  • Triggering command: /tmp/go-build943415157/b001/exe/govulncheck /tmp/go-build943415157/b001/exe/govulncheck ./... --threads=4 --no-sublanguage-file-coverage --no-calculate-baseline --overwrite --language go --build-mode autobuild --source-root /home/REDACTED/work/queue/queue -p x64/src/net -trimpath ux_amd64/vet -I /tmp/go-build12221.0.8+9-LTS -I ux_amd64/vet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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