Add prototype browser-based CAD parameter editor

[BenCaunt]

Motivation

• Provide a human-friendly way to edit CAD-driving parameters so non-coders (or LLM-driven workflows) can adjust designs without hand-editing Python source.
• Prototype a minimal, dependency-free interface as a first step toward a graphical sketch/parameter editor for the CAD project.

Description

• Add synthcad/sketch_editor_cli.py, an AST-backed CLI that discovers top-level uppercase constants and serves a small HTTP API (/api/schema, /api/apply) plus an embedded HTML/JS frontend for in-browser editing of numeric/string/tuple literals.
• Implement in-place source updates via apply_constant_updates by mapping AST assignment ranges back to file text and replacing targeted assignments with repr-serialized values.
• Register the CLI entry point synthcad-sketch-editor in pyproject.toml and add unit tests in tests/test_sketch_editor_cli.py covering discovery and update behavior.

Testing

• Ran uv run pytest tests/test_sketch_editor_cli.py to exercise the discovery and update functions.
• The test run completed successfully with all tests passing (2 passed).

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Codex Task

[github-actions]

SynthCAD CAD review

Compared 50cc8c6e6505 to def33044b4bf for flat-disk-robot.

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