Add Align cylinders tool for shaft-into-hole placement

[trailcode]

Summary

Add a one-shot Align cylinders tool so a shaft can be placed into a hole (or the reverse) by picking two cylindrical faces, coaxially aligning them, then dragging insert depth along the shared axis before baking the transform.

This is not a persistent assembly mate. Placement bakes into BREP like Move / Rotate (SetLocalTransformation preview -> bake_transform_into_geometry + Shape_geom_delta).

Problem

• Users can Move / Rotate solids freely, but there is no way to snap a rod into a hole by cylindrical axes.
• Hole and shaft geometry already exist as OCCT cylindrical faces; the app did not extract axis/radius or offer an insert-align workflow.

Implemented scope

Behavior:

• Mode Shape_cyl_align, default hotkey J (mode.cyl_align, remappable).
• Pick moving cylindrical face, then fixed cylindrical face on a different solid.
• Coaxial align; drag axial depth (or Tab for exact depth); LMB / Enter finalize; Esc cancel.
• Options Flip direction reverses axis sense.
• Radius mismatch logs a warning but still places.
• Face selection mode while picking; dynamic AIS highlight off during depth drag.

Code:

• cylinder_from_face / cyl_align_trsf in utl_geom
• Shp_cyl_align operation
• Mode / hotkey / toolbar / Options / Occt_view wiring

Documentation:

• docs/usage.md (Align cylinders section + hotkeys)
• src/doc/shape.md, src/doc/gui.md
• CHANGELOG.md [Unreleased]

Acceptance criteria

• Enter tool via J or toolbar; Face selection active for picks
• Two-face pick: first moves, second fixed; reject non-cylinder / same-shape second pick
• Coaxial preview then axial depth drag; Tab depth; Flip direction; bake + undo
• Docs + CHANGELOG + remappable hotkey defaults
• Manual smoke on rod + hole solids (desktop Release)

Out of scope (v1)

• Persistent mates / assembly constraints
• Auto flush to planar end faces
• Script bindings
• Fit / interference checking beyond radius warning

Related

• Branch: Trailcode/shp-cyl-align