Speed up path extrusion point generation

[KRRT7]

Summary

• replace per-point DCplxTrans construction and NumPy angle conversion with direct normal-vector offset math
• preserve existing default end-angle behavior and zero-length segment handling

Benchmark

• extrude_path improved from about 99ms to about 52ms median in benchmarks/hotspots.py local runs
• extrude_path_dynamic improved from about 151ms to about 63ms median in benchmarks/hotspots.py local runs

Verification

• uv run ruff check src/kfactory/enclosure.py
• uv run pytest tests/test_extrude.py tests/test_enclosure.py tests/test_factories_utils.py -q
• uv run pytest -q passed on the combined local optimization branch

Note: local ty on macOS is fixed separately in PR #1001.

[codecov]

Codecov Report

❌ Patch coverage is 90.38462% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.03%. Comparing base (f61117b) to head (eecff29).

Files with missing lines	Patch %	Lines
src/kfactory/enclosure.py	90.38%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1004      +/-   ##
==========================================
- Coverage   71.05%   71.03%   -0.02%     
==========================================
  Files          72       72              
  Lines       14809    14810       +1     
  Branches     2882     2884       +2     
==========================================
- Hits        10523    10521       -2     
- Misses       3387     3389       +2     
- Partials      899      900       +1     

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[sebastian-goeldi]

not reviewing pure LLM PRs

[sebastian-goeldi]

what's the speedup here? this is usually not in a very critical path, so small differences in runtime are probably not worth the headache if something's wrong