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>

docs/book/src/introduction.md

@@ -21,8 +21,8 @@ also script, test or hand to an agent.
 SolidCraft is early. Sketching, solid modelling, parameters, components with joints, sheet metal
 and a plastic-enclosure subset work; surfaces, drawings, CAM and simulation are deferred. The
 [roadmap](https://github.com/bherbruck/solidcraft/blob/main/ROADMAP.md) has the details, and
-[command parity](dev/parity.md) and the [reference tests](dev/oracle.md) measure how far along it
-is.
+the [feature list](dev/features.md) lists every command by area, and the
+[reference tests](dev/oracle.md) check modelling results against analytic and FreeCAD values.
 
 Existing `.solvecraft` designs and `solvecraft-cli` commands keep their names and behavior.
 
@@ -30,5 +30,7 @@ This book has two halves: the **user guide** for people modelling with SolidCraf
 **developer guide** for people working on it. The [command reference](reference/commands.md) is
 generated from the code on every build.
 
-SolidCraft is licensed MIT OR Apache-2.0. It is a clean-room implementation and is not affiliated
-with Autodesk; Fusion is a trademark of Autodesk, Inc.
+SolidCraft is licensed MIT OR Apache-2.0. It is independent: behaviour is designed from public
+documentation, general CAD conventions and user feedback, and reference tests use analytic
+values and open-source tools. SolidCraft is not affiliated with Autodesk; Fusion is a trademark
+of Autodesk, Inc.