Retire legacy reference data and the external command catalog (#302)

- Remove xtask/data/fusion-catalog.tsv and xtask/data/fusion-ids.tsv.
- Remove the legacy command-id table (crates/engine/src/legacy_ids.rs) and its use in
  find_command and in the shortcut, recents and pinned-command loaders. Only SolidCraft's
  dotted ids name commands; any other id is an unknown command.
- Boundary Fill's id becomes solid.boundary_fill.
- Replace the parity report with SolidCraft's own feature checklist: `cargo xtask features`
  writes docs/features.md from the command registry.
- docs/oracle.md, docs/step-import.md (corpus section) and docs/iges-import.md: reference
  results are being rebuilt on analytic and open-source (FreeCAD) values; see #292.
  `cargo xtask oracle` and `cargo xtask step-corpus [--iges]` write these placeholders.
- AGENTS.md, CLAUDE.md, CONTRIBUTING.md, README.md, ROADMAP.md and the book describe
  SolidCraft as independent, with reference tests on analytic values and open-source tools,
  and agents do not drive or extract data from commercial CAD products.


Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/mod.rs

@@ -1,6 +1,6 @@
 //! The command registry. Ids are SolveCraft's own dotted ids (`solid.extrude`,
 //! `sketch.rectangle.two_point`); the toolbar placement (`tab`, `panel`) follows the familiar
-//! Design workspace layout. Ids used before the rename still resolve (`legacy_ids`).
+//! Design workspace layout.
 
 /// The params-doc note of every command that adds sketch geometry (see `sketch::created`).
 macro_rules! created_doc {
@@ -180,7 +180,5 @@ pub fn command_specs() -> Vec<&'static CommandSpec> {
 
 pub fn find_command(id: &str) -> Option<&'static CommandSpec> {
     let all = command_specs();
-    // Ids from before the rename still find their command.
-    let id = crate::legacy_ids::current_id(id);
     all.iter().find(|c| c.id == id).or_else(|| all.iter().find(|c| c.id.eq_ignore_ascii_case(id))).copied()
 }