docs: explain Workplane tag and end usage

[pranjalbhatia710]

Closes #666.

This adds a small Workplane docs section for the two stack helpers called out in the issue:

• explains how end() returns to the parent Workplane after a selection
• explains how tag() stores a stable Workplane reference in the modelling context
• shows a short example that tags mating-style faces, returns to the base part, and later selects from the tagged Workplanes with the selector tag argument

Validation:

• python3 AST parse of the added code snippets
• git diff --check

I could not run the full Sphinx docs build locally because the checkout does not currently have CadQuery's runtime/doc dependencies installed (import cadquery fails on missing runtype).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.70%. Comparing base (9633409) to head (d8e7cef).
⚠️ Report is 14 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2044      +/-   ##
==========================================
+ Coverage   95.64%   95.70%   +0.05%     
==========================================
  Files          30       30              
  Lines        8962     9447     +485     
  Branches     1328     1406      +78     
==========================================
+ Hits         8572     9041     +469     
- Misses        240      252      +12     
- Partials      150      154       +4     

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[jmwright]

@pranjalbhatia710 Thanks for taking this on.

To fully close #666 two more pieces are needed in the docs:

1. end(n) with a count - end takes an integer, and the issue mentions wanting to walk back through a multi-step selection with something like .end(3).
2. workplaneFromTagged - Where a tag is used to create a new workplane.

This could be merged as-is without closing #666 but it would be nice to have mentions/examples of those two items.

The section titled Chaining is right after your section, but it conceptually introduces tags in its last sentence. That would be a nice transition into your section, so I would suggest moving your section directly after Chaining.

[pranjalbhatia710]

Thanks for the review — I pushed f70dee7 to cover both remaining pieces from #666:

• notes that end(n) can walk back multiple parents, with an .end(3) example
• adds a workplaneFromTagged("right_face") example showing how to start another feature from a tagged workplane

Validation:

git diff --check
# no output

I kept this in the existing Tagging Workplanes section so it does not expand the separate Chaining section further.

[pranjalbhatia710]

Thanks — I pushed d8e7cef to apply the placement suggestion as well. The Chaining overview now stays first, and the Tagging Workplanes section follows it directly as the transition into tags/end/workplaneFromTagged examples.

Validation:

git diff --check
# no output