feat(delay): add Delay queue

[adrianbrad]

Summary

New Delay[T comparable] queue where each element becomes dequeuable at a deadline computed by a caller-supplied function at Offer time. Satisfies the existing Queue[T] interface — no separate interface introduced.

API

func NewDelay[T comparable](
    elems []T,
    deadlineFunc func(T) time.Time,
    opts ...Option,
) *Delay[T]

// Queue[T]: Get / Offer / Reset / Contains / Peek / Size / IsEmpty /
//            Iterator / Clear
// Extras:   GetWait / MarshalJSON

Implementation notes

• Min-heap by deadline, written directly on []delayed[T] rather than via container/heap. pprof on the Get_Offer benchmark showed container/heap's any boxing accounted for >75% of allocations and ~50% of CPU in GC. Typed push / pop / up / down keep the steady-state offer-then-get loop at 0 allocs.
• GetWait uses sync.Cond + time.AfterFunc so "head is due" and "state changed" compose under a single Wait, matching the cond-var idiom used by Blocking.
• Peek returns the head regardless of whether its deadline has passed — matches java.util.concurrent.DelayQueue.peek.
• Panics on nil deadlineFunc or negative capacity, consistent with NewPriority.

Benchmarks

BenchmarkDelayQueue/Peek          4.1 ns/op     0 B/op   0 allocs/op
BenchmarkDelayQueue/Get_Offer    52.4 ns/op     0 B/op   0 allocs/op
BenchmarkDelayQueue/Offer        63.5 ns/op   315 B/op   0 allocs/op

(B/op on Offer is amortized slice growth from unbounded pushes in the benchmark; no per-op alloc.)

Test plan

• go test -race -shuffle=on .
• go test -coverprofile — 100% statements
• golangci-lint run passes locally
• Benchmark verified with pprof (boxing eliminated)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (5bacf9d) to head (4c2b1b6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main       #61    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            5         6     +1     
  Lines          483       639   +156     
==========================================
+ Hits           483       639   +156     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.