Enhance code quality and documentation across the intervals_icu_* crates

chore: bump package version to 2.4.1 for intervals_icu_client and intervals_icu_mcp

feat: add rate limit handling and warnings to API error responses

chore: Updated rmcp

test: add fatigue alert test for TSB boundary condition

fix: update range syntax and improve polarisation z2_pct handling in alerts

fix: ensure polarisation z2_pct is present before building alerts

refactor: change PolarisationMetrics fields to Option types for better handling of missing data

bump version to 2.4.0 for intervals_icu_client and intervals_icu_mcp

Refactor tests to use MockIntervalsClient for event handling

fix: address 6 code review issues — monotony cap, decoupling EF, intervals filter, and 3 style fixes

refactor: improve markdown formatting in ModifyTraining and PlanTraining handlers

docs: document compact markdown conventions in SPEC.md

test: fix integration tests for compact markdown output

refactor: compact markdown in analyze_training handler