fix: bound countersink cuts by explicit depth

[RanaPriyansh]

Description

Fixes #1653.

cskHole can cut below an explicit shallow depth because its countersink cone extends to its full tip.

Clip the cone to the requested depth before combining it with the bore. The full cone remains in use for deeper and through holes.

Tests

• Added volume and material checks for shallow, near-tip, deep, through, and 45-degree holes. Added close-diameter controls.
• The focused tests pass. Fork Black passes.
• The full local suite has 894 passes, three skips, and one failure. The same test_interpPlate volume mismatch occurs on the exact base.
• Mypy reports the same OCP missing-stub errors on the exact base and this change.

A small local timing comparison measured shallow cuts at 6.7–6.9 ms before and 8.0 ms after this change. Deep and through-hole timings overlapped. The shallow path performs one additional Boolean intersection.

Codex used.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.81%. Comparing base (c11b3f9) to head (0570574).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2103      +/-   ##
==========================================
+ Coverage   95.80%   95.81%   +0.01%     
==========================================
  Files          30       30              
  Lines        9589     9592       +3     
  Branches     1439     1440       +1     
==========================================
+ Hits         9187     9191       +4     
  Misses        247      247              
+ Partials      155      154       -1     

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