release: v0.1.5 — Go 1.27+ version bump, resolve all lint issues

[kolkov]

Summary

• Update Go version requirement from 1.25+ to 1.27+ in README
• Resolve all 16 golangci-lint issues (staticcheck, gosec, nolintlint, prealloc, gocognit)
• Update CHANGELOG with v0.1.5 entry and complete version history

Changes

Lint fixes (16 issues → 0)

• staticcheck: fmt.Fprintf instead of WriteString(fmt.Sprintf) in SSE event
• gosec: safe int→uint16 via bounds clamp for WebSocket close code
• nolintlint: remove 2 unused //nolint:gosec directives
• gocognit: annotate Hub.Run() select loop
• prealloc: slices.Concat for test frame construction (11 instances)

Documentation

• README: Go 1.25+ → Go 1.27+ (title, requirements, features)
• CHANGELOG: v0.1.5 entry + complete version history

Test plan

• go build ./... clean
• go test -short ./... all pass
• golangci-lint run — 0 issues
• gofmt -l . — clean

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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