Update dependencies and modernize code for Go 1.24

[umputun]

Summary

Updates dependencies and modernizes codebase for Go 1.24, plus fixes various documentation issues.

Changes

Code modernization:

• Update golang.org/x/sync to v0.19.0, golang.org/x/time to v0.14.0
• Enable modernize linter, bump golangci-lint to v2.7
• Use range over int syntax throughout codebase
• Replace interface{} with any in middleware

Documentation fixes:

• Fix Go version requirement (1.23+ to 1.24+)
• Fix trailing comma in Quick Start example (would not compile)
• Fix WithCompleteFn to WithWorkerCompleteFn with correct signature
• Fix dependencies claim (now mentions golang.org/x packages)
• Clarify work distribution (shared channel vs random accumulator)
• Clarify completion callback behavior (skipped on context.Canceled only)
• Clarify Dropped metric is user-incrementable
• Clarify AvgLatency uses max ProcessingTime across workers
• Add CLAUDE.md project documentation

[Copilot]

Pull request overview

This PR modernizes the codebase for Go 1.24, updates dependencies, and fixes various documentation issues. The changes leverage Go 1.23+ features like range-over-int syntax and replace legacy interface{} with the any type alias.

• Updates golang.org/x/sync to v0.19.0, golang.org/x/time to v0.14.0, and testify to v1.11.1
• Adopts modern Go syntax: range-over-int loops and any type throughout the codebase
• Fixes multiple documentation issues in README.md including incorrect function signatures, clarifications on work distribution, metrics behavior, and completion callbacks

Reviewed changes

Copilot reviewed 19 out of 27 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
go.mod	Updates Go version to 1.24.0 and bumps dependency versions
go.sum	Updates dependency checksums for new versions
pool.go	Modernizes code using max() built-in function
pool_test.go	Adopts range-over-int syntax in test loops
middleware/middleware.go	Replaces interface{} with any in Recovery function signature
middleware/middleware_test.go	Replaces interface{} with any in test variables and function signatures
metrics/metrics_test.go	Adopts range-over-int syntax in concurrent test loops
examples_test.go	Adopts range-over-int syntax in example code
bench_test.go	Adopts range-over-int syntax in benchmark loops
README.md	Fixes trailing comma in Quick Start, corrects function signatures, clarifies documentation on work distribution, metrics, and completion callbacks
CLAUDE.md	Adds comprehensive project documentation for Claude Code
.golangci.yml	Enables modernize linter
.github/workflows/ci.yml	Bumps golangci-lint to v2.7
examples/*/go.mod	Updates Go version to 1.24.0 and adds toolchain directive for all example modules
examples/*/go.sum	Updates dependency checksums for example modules

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