refactor(examples): rewrite with classic problems & meaningful names

[noneback]

• simple: MapReduce word count (split→map×4→shuffle→reduce×2→merge)
• conditional: event severity routing (ingest→classify→3 processing paths)
• loop: web crawler with retry & exponential backoff
• ci_pipeline: CI/CD with nested subflows (build→test→deploy)
• priority: fix typo, remove internal utils dependency
• fibonacci: fix output label
• parallel_merge_sort: add WithProfiler, remove internal pprof
• README: add Quick Start with MapReduce, fix merge sort closure bug
• Regenerate all SVGs with meaningful node names

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.28%. Comparing base (9093057) to head (a368996).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #108   +/-   ##
=======================================
  Coverage   89.28%   89.28%           
=======================================
  Files          16       16           
  Lines         812      812           
=======================================
  Hits          725      725           
  Misses         63       63           
  Partials       24       24           

Flag	Coverage Δ
unittests	89.28% <ø> (ø)

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