Add hollowpositioningarmtube model contract

[imrishabh18]

Add hollowpositioningarmtube, a reusable parametric contract for hollow positioning arm tubes used in lamp and camera assemblies. The model supports outside/bore diameters, two straight lengths, a circular bend and optional annular ribs. It describes the installed envelope; wires, mounting fittings and mechanical load ratings remain outside this model.

hollowpositioningarmtube_od6mm_id4mm_start38mm_end112mm_radius60mm_angle90_pitch2.25mm_depth0.25mm

The folder-local schema, parser and typed registration expose hollowPositioningArmTubeModelPropsSchema, getHollowPositioningArmTubeDimensions and getHollowPositioningArmTubeFrame, with corresponding HollowPositioningArmTube types. The parameter documentation is in docs/hollowpositioningarmtube.md. Public model names, paths, examples and tests consistently use hollowpositioningarmtube.

The paired renderer is jscad-electronics#442, which supplies the three labeled four-view snapshots below and consumes this contract's immutable package preview at 394ffb8. Merge and release this contract before replacing that preview with a stable dependency in the renderer.

Validation:

• All 84 contract tests pass with Bun 1.3.2, including unit normalization, parameter validation, model registration and centerline/dimension helpers.
• Typecheck, format check and package build pass.
• CI passes at 394ffb8; the package preview is published.
• All three paired renderer snapshots pass comparison. Mesh hashes match their previous versions, confirming the naming update preserves geometry.

90-degree bend:

Straight ribbed tube:

Smooth U bend:

[tscircuitbot]

---

Thank you for your contribution! 🎉

PR Rating: ⭐⭐⭐
Impact: Major

Track your contributions and see the leaderboard at: tscircuit Contribution Tracker

---