[MasoudMiM]

Detect a full-revolution spherical CAP and rebuild it as editable PartDesign history. A convex cap standing on a face is a spherical boss (dome), a concave cap cut into a face is a spherical seat (socket). PartDesign has no sphere primitive, so the executor revolve-builds the cap: a circular-arc profile sketched on a vertical plane through the axis, spun 360 deg as a PartDesign::Revolution (additive dome) or PartDesign::Groove (subtractive seat), the apex placed exactly.

Scope: smooth domes, truncated (flat-topped) domes, and smooth sockets. Full spheres and flat-bottomed sockets are out of scope (left unassigned, per the unplanned doctrine).

Pole-cap tessellation artifact (the FreeCAD socket regression): the apex is read off the patch's high-elevation end (r_hi ~ 0 => the smooth pole, a real r_hi => a flat truncation). FreeCAD's tessellator peels a boolean-cut socket's pole off as a separate tiny cone cap, so the sphere patch stops just short of the pole and reads a small nonzero r_hi — previously misclassified as a flat-bottom socket and dropped. The pole cap (a cone whose apex sits at the sphere's geometric pole, opening back toward the rim) is now recognized so the socket is still detected and rebuilt smooth. A truncated dome's flat top, when the segmentation keeps it as a separate plane, is recorded as provenance and excluded from the base extent (like the cylindrical boss cap).

Changes

• core/features.py — the sphere_boss / sphere_seat detection rule (+ _is_concave_sphere, _plane_hole_loops_on_sphere, _outer_loop_is_disk_on_sphere, pole-cap recognition).
• core/history.py — the SphereOp plan op, dispatch, and the sphere-boss base-extent exclusion.
• build.py — the _add_sphere revolve executor branch (Revolution / Groove).
• core/solidify.py — the headless _sphere_cap (truncation-capable).
• tests/test_sphere.py — 26 new tests (detection / planning / round-trip).
• scripts/freecad_smoke_test.py — dome + socket smoke cases.
• Docs: README (capabilities + limitations), CHANGELOG (Unreleased), ROADMAP (Phase 2 item 2 -> done).

Verification

• Headless suite: 551 passed, 1 xfail (no regressions).
• FreeCAD smoke test: ALL CHECKS PASSED — dome via Revolution (20435.62 vs 20435.63), socket via Groove (19564.38 vs 19564.37).

Closes Phase 2 item 2 (spheres) of the roadmap.