feat(editor): code completion from the SDK; ( writes the required name= parameters

[NiJingzhe]

Why

The cell editor had no completion for the SDK: it is plain CodeMirror with the stock Python language support, which only knows Python keywords and names already in the file. scad. is a runtime module, so nothing listed its functions, and a call's parameters had to be looked up elsewhere.

What

• GET /api/sdk (editor/apiindex.py): the running package's public API as data (name, kind, parameters with required/optional/*args/default, first docstring paragraph), read with inspect so it cannot drift from the code. Namespaces: scad, scad.ql, scad.std.<module>. About 100 KB (20 KB gzipped), fetched once.
• editor-web/src/lib/sdk-complete.ts (CodeMirror):
  • scad., scad.ql., scad.std.gear., ql. / Q. list functions with their signature; the side panel shows every parameter with its default and the docstring.
  • Accepting a function, or typing ( after a known name, writes the call with every required parameter as name= placeholders: scad.make_box_rsolid(width=, height=, depth=). Tab moves to the next parameter (and accepts a highlighted suggestion first). Positional-only and *args parameters get a hint placeholder.
  • Inside a call, the parameters not given yet complete as name= (required first, above Python's builtins).
  • Accepting a completion on a name that already has parentheses changes only the name.
• A bug that made snippets unusable: the editor wrapper rebuilt its CodeMirror configuration on every render (a fresh onChange and basicSetup object each time), which drops a snippet in progress. Both are stable now (CellEditor, ModuleView).
• Popup styled for both themes.

Checked

• test/test_editor.py (new ApiIndexTest: required parameters, *args, classes without private fields, namespaces, the endpoint): 43 passed.
• In the real editor, with a browser: scad.make_box_r + Tab -> width=, height=, depth=, then 10 Tab 20 Tab 30 -> width=10, height=20, depth=30; scad.fillet_rsolid( typed by hand -> solid=, edges=, radius=; scad.ql.fac and scad.std.gear.make_sp list the right names; , bo after the required parameters offers bottom_face_center= first; accepting on an existing call changes only the name; dark and light.

Not covered

• Methods on values (selector.where(...)) and variables are not completed; only names reached through scad, scad.ql/ql/Q and scad.std.<module>.
• The notebook may import the SDK under another alias; only scad, ql and Q are recognized.