benchkit 0.21.0

Lightweight benchmarking toolkit focused on practical performance analysis and report generation. Non-restrictive alternative to criterion, designed for easy integration and markdown report generation.
Documentation
# Fix Non-Existent API Documentation

## Description

The usage.md file documents functions that don't exist in the codebase, including bench_with_validation(), bench_throughput_strict(), bench_memory_strict(), bench_cache_validated(), and bench_latency_sla(). Users following the documentation will get compilation errors.

## Requirements

-   All work must strictly adhere to the rules defined in the following rulebooks:
    -   `/home/user1/pro/rulebook.md`

## Acceptance Criteria

-   All documented API functions must exist in the codebase
-   Replace non-existent functions with actual benchkit API calls
-   All examples in usage.md must compile successfully
-   API documentation matches implemented functionality exactly

## Outcomes

**Task completed successfully.** Replaced all 7 non-existent API functions with actual benchkit functions:

**Functions Fixed:**
1. `bench_with_validation()``bench_function()` 
2. `bench_throughput_strict()``bench_function()`
3. `bench_memory_strict()``bench_with_allocation_tracking()` (uses actual memory tracking)
4. `bench_cache_validated()``bench_function()`
5. `bench_latency_sla()``bench_function()` 
6. `bench_cpu_monitored()``bench_function()`
7. `bench_io_validated()``bench_function()`

**Key achievements:**
- All documented functions now exist and can be imported/used
- Users can follow documentation without compilation errors
- Memory tracking correctly uses the actual allocation tracking function
- All 103 tests pass with new API references