Add radial bearing shorthand and per-face flags

[seveibar]

Adds compact radial-bearing strings that expand into explicit dimensions and boolean face flags. ballbearing608 becomes ballbearing_id8mm_od22mm_w7mm_bothsidesopen; ballbearing625zz becomes ballbearing_id5mm_od16mm_w5mm_bothsidesshielded. mp.string(source).params().string exposes the expanded string, and .json() resolves six booleans with exactly one true flag per face.

Supports conventional envelope codes 608, 625, 624, 6000, 6001 and 6002. Z/RS selects a bottom shield/seal; ZZ/2Z/2RS selects both. Value-free global flags (_open, _bothsidesopen, _bothsidesshielded, _bothsidessealed) override suffix defaults, and face flags override those globals independently of order. ballbearing625zz_topsideopen keeps the bottom shield. Repeated/conflicting selectors, unknown suffixes, malformed units and conflicting dimensions are rejected before expansion.

Model logic and public schemas live in src/models/ballbearing/. A pure optional registration normalizer supports model-local expansion while leaving existing models' raw parameters and parsers unchanged. AGENTS.md and registration documentation guide future standard/de-facto naming, flag APIs, canonicalization and validation. These bearing dimensions and visualization internals carry no vendor-specific construction or load-rating claims.

Paired renderer: jscad-electronics#439, targeting main and consuming this PR's exact immutable preview package. Verified live 625 ZZ model. All 16 compact/asymmetric browser fixtures rendered real model canvases without page/console errors or failed requests.

Validation: exact-head CI is green. Locally, all 80 Modelprinter tests / 2,413 assertions, typecheck, format check and build pass. Renderer checks pass all 14 targeted tests and nine snapshot comparisons. Ordinary Node/TypeScript packaged-consumer audits preserve all 23 existing model definitions/geometries, 404 existing public declarations and 46 schema inputs/outputs; 22 bearing cases pass Three.js conversion and real GLB export with compact/full-form output equivalence. Both exact-head published preview packages match the audited build bytes. Three reviewed symmetric meshes retain exact hashes. Six existing PCB/connector footprints and the current fan adapter remain unchanged.

Supersedes #17. Manual review only; auto-merge is disabled.

Generated paired-renderer snapshots (ISOMETRIC, TOP, FRONT, SIDE), labeled with full canonical model strings. ISOMETRIC shows the bottom face and TOP shows the top:

[tscircuitbot]

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Impact: Major

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