New skill proposal: dfam-check — printability rules for meshes

[knewnothing-git]

Hi maintainers,

I'd like to propose adding a dfam-check skill that fills a gap between $cad (generates meshes) and $gcode (slices them): checking whether the mesh is actually printable for the target AM process before it gets sliced.

What it does

Measures mesh files (.stl, .obj, .ply, .3mf) against DfAM rules from ISO/ASTM 52910 and published process design guides:

Overhang angle histogram (build-plate contact excluded)
Wall thickness field via ray-cast sampling
Support-volume upper-bound estimate
Six axis-aligned orientation candidates ranked by support area and build height

Reports facts only — the workflow does the ✅/❌/❓ comparisons against a limits table per process (FDM, SLS, SLA/DLP, metal PBF, MJF), same pattern as $sendcutsend.

Why it fits

Today an agent can go $cad → $gcode → print with no printability gate. $sendcutsend is the sheet-metal preflight; there's no equivalent for FDM/SLS/SLA/metal AM before slicing. dfam-check would be that gate, and would hand off to $cad for regeneration and $cad-viewer for visual inspection.

Status

Working prototype, tested on three fixtures (thin-walled box, cantilevered bracket, solid block) — measurements match the planted defects exactly (0.6mm walls flagged, 1200mm² of 0° overhangs located, 226% support ratio on the bracket).

Structure matches the $sendcutsend / $gcode convention: SKILL.md + references/process-limits.md + scripts/dfam_tool.py + agents/openai.yaml + MIT LICENSE.

Would this fit the roadmap? Happy to open a PR against develop if there's interest — CONTRIBUTING.md is clear on the flow.

Thanks!