feat(microscope-slide-holder): explicit fit_clearance_slide behind the legacy material injection

[aldoruizluna]

What changed

Digital Twins MES, Phase 2 wave 2, lane W2-MAT. Owner ruling: "flag now, flip later". This PR is the commons side that lets yantra4d turn RENDER_MATERIAL_INJECTION off without losing function.

• libs/microscope-slide-hyperobject/slide.scad (the vendored library, which rides with this cartridge): slide_slot_width() now adds fit_clearance_slide (mm, default 0). The legacy mat_clear_slide is undef unless the platform injects it with -D, and an injected value wins (_legacy_or()). Every render made with the flag on is therefore unchanged. The legacy branch is commented REMOVE AT THE FLIP. The header is the same text as microscope-slide-hyperobject's PR; the vendored file's rib module is untouched.
• project.json: declares fit_clearance_slide (slider 0 to 1 mm, step 0.01, group tolerance, advanced visibility, labels in en/es/fr/pt), visible in the OpenSCAD modes that call slot_width(): box, staining_rack and cabinet_drawer.

What the legacy injection does to this cartridge today (measured)

• -D mat_clear_slide does reach geometry, even through use <slide_lib.scad> → include <libs/…/slide.scad>. The -D render is identical to a render with the literal edited in the source.
• It moves box (base and lid) and cabinet_drawer (drawer and shell) at every SCAD preset.
• staining_rack is inert at defaults and at every preset, because of its 5 mm minimum pitch. It is reachable only for thick slides near the slider maxima.
• tray never calls slot_width().
• mat_shrinkage_*, mat_clear_press, mat_clear_loose and thermo_* are inert here.
• The CadQuery modes (main.py) read none of them, and this PR does not touch main.py.

GOC-1 mapping

• fit_clearance_slide passes the GOC-1 variables denylist; I checked it against generator-output.schema.json. After the flip, a resolved sliding-fit clearance reaches this cartridge as a geometry-named number in variables, and legacy_physical_inputs stays empty.
• The manifest default (0.0) equals the library literal. With RENDER_INJECT_FULL_PARAMS on, the geometry is unchanged (row A4).

Evidence

I rendered locally with OpenSCAD 2026.02.13 and --backend=Manifold. Geometry was compared as volume, AABB, body count and the sha256 of the sorted unique vertex set rounded to 1e-4, never as STL bytes.

The matrix is 6 SCAD targets (box base and lid, tray, staining_rack, cabinet_drawer drawer and shell) × 9 parameter sets (defaults plus the 8 SCAD presets) = 54 rows. Each row has 6 checks, 324 comparisons in total, with 0 mismatches:

Check	Meaning
A0 after, no material = before, no material	today's no-material render is unchanged
A4 after, fit_clearance_slide=0.0 = before, no material	explicit defaults (injection OFF) = today's no-material render
A1 after, bambu-tpu-95a injected = before, TPU injected	geometry is unchanged with injection ON
A5 after, sinterit-pa12-smooth injected = before, PA12 injected	same, second material
A2 after, explicit fit_clearance_slide=0.1 = before, TPU injected	the explicit parameter carries the function
A3 after, TPU injected plus explicit 0.5 = before, TPU injected	the injected value wins

For example, at defaults box_base measures 86312.824 mm³ with no material and 86893.175 mm³ with TPU, and cabinet_drawer shell measures 235996.166 mm³ and 241873.840 mm³.

y4d-spec check ./microscope-slide-holder --render --require-openscad --parity --openscad-path libs --openscad-path .:

• at the CI pin 3ff3736: cartridges=1 failures=0 notes=0 geometry=verified renders=19 presets=9 skipped=0 parity=0/0 ok
• at the P2-S head (510efba): failures=0 notes=19. All 19 notes are pre-existing default-drift notes on other parameters; unmodified main gives the same notes=19. None concerns fit_clearance_slide.

CI status

Green on Linux CI (own runners) at the time of writing: manifest conformance (all cartridges) passed in 38s, render scope passed, and render (cartridges changed in this PR: microscope-slide-holder) passed in 2m18s.

Deviations / notes

• No target_material change; this cartridge never declared it.
• The vendored libs/microscope-slide-hyperobject/{project.json,slide.py,README.md} are not re-synced. The holder executes only the vendored slide.scad.

🤖 Generated with Claude Code