Replace model geometry enums with boolean flags

[seveibar]

Geometry, placement, and handedness selectors now use bare flags and boolean JSON properties across 23 existing models. For example, plainbushing_id8mm_od12mm_l20mm_plainclosed resolves to plainClosed: true, while hexbolt_m4_l20mm_hex_fullthread_lefthanded exposes hex, fullThread, and leftHanded booleans.

This removes the old enum selector tokens and JSON properties for bushings, extrusion profiles, screw drives, mounting styles, spring construction, gasket/strip profiles, gear handedness, FlexScreen placement, NEMA geometry/wire modes, and sheet metal forms/hole shapes. Repeated, valued, and conflicting flags are rejected. Defaults, dimensions, catalog/standard identifiers, and coordinate arguments retain their meanings. The flag-to-enum expansion hooks are removed.

Validation: 301 tests pass, including standalone retired-selector rejection, direct-parser boundaries, boolean defaults/schema roundtrips, and conflicts. bun run typecheck, bun run format:check, and bun run build pass.

Paired renderer PR: tscircuit/jscad-electronics#501

[tscircuitbot]

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