Add persistent sketch-constraint system (ocs_gcs port) and named-parameters handoff docs

Ports FreeCAD's planegcs 2D geometric constraint solver to Rust as a new
crates/ocs_gcs workspace member, and wires it into the document/scene model
as a persistent SketchConstraintSet: Coincident, Horizontal/Vertical,
Parallel/Perpendicular, Equal, Tangent, Distance, Angle and Radius
constraints that re-solve live (including mid-drag, not just on release),
render glyphs and a DOF badge, flag conflicts with a one-click resolver
pill, and round-trip through save/load via an XRecord blob.

Also includes docs/command_reference.md (a statically generated reference
of every registered command and its prompt sequence) and
docs/named_parameters_design.md + docs/backlog.md, which hand off the next
queued feature (a named-parameter/expression table) and consolidate every
deliberate scope-down and open gap found along the way, so a fresh session
has a complete starting point.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

Cargo.lock

@@ -39,6 +39,7 @@ dependencies = [
  "objc2-app-kit 0.2.2",
  "objc2-foundation 0.2.2",
  "ocs_doc_api",
+ "ocs_gcs",
  "ocs_plugin_api",
  "open",
  "printpdf",
@@ -323,6 +324,15 @@ version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2a4385e2e34eb35d6b3efe798b9eb88096925d87726c0798709bf56d9ed84af3"
 
+[[package]]
+name = "approx"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cab112f0a86d568ea0e627cc1d6be74a1e9cd55214684db5561995f6dad897c6"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "arbitrary"
 version = "1.4.2"
@@ -3178,6 +3188,16 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "matrixmultiply"
+version = "0.3.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f607c237553f086e7043417a51df26b2eb899d3caff94e6a67592ff992fedc7"
+dependencies = [
+ "autocfg",
+ "rawpointer",
+]
+
 [[package]]
 name = "maybe-rayon"
 version = "0.1.1"
@@ -3358,6 +3378,33 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "nalgebra"
+version = "0.33.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d43ddcacf343185dfd6de2ee786d9e8b1c2301622afab66b6c73baf9882abfd"
+dependencies = [
+ "approx",
+ "matrixmultiply",
+ "nalgebra-macros",
+ "num-complex",
+ "num-rational",
+ "num-traits",
+ "simba",
+ "typenum",
+]
+
+[[package]]
+name = "nalgebra-macros"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "254a5372af8fc138e36684761d3c0cdb758a4410e938babcff1c860ce14ddbfc"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "ndk"
 version = "0.9.0"
@@ -3905,6 +3952,13 @@ dependencies = [
  "toml 1.1.3+spec-1.1.0",
 ]
 
+[[package]]
+name = "ocs_gcs"
+version = "0.1.0"
+dependencies = [
+ "nalgebra",
+]
+
 [[package]]
 name = "ocs_plugin_api"
 version = "0.2.1"
@@ -4607,6 +4661,12 @@ dependencies = [
  "objc2-quartz-core 0.3.2",
 ]
 
+[[package]]
+name = "rawpointer"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60a357793950651c4ed0f3f52338f53b2f809f32d83a07f72909fa13e4c6c1e3"
+
 [[package]]
 name = "rayon"
 version = "1.12.0"
@@ -5015,6 +5075,15 @@ version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
 
+[[package]]
+name = "safe_arch"
+version = "0.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96b02de82ddbe1b636e6170c21be622223aea188ef2e139be0a5b219ec215323"
+dependencies = [
+ "bytemuck",
+]
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -5228,6 +5297,19 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "simba"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c99284beb21666094ba2b75bbceda012e610f5479dfcc2d6e2426f53197ffd95"
+dependencies = [
+ "approx",
+ "num-complex",
+ "num-traits",
+ "paste",
+ "wide",
+]
+
 [[package]]
 name = "simd-adler32"
 version = "0.3.10"
@@ -6532,6 +6614,16 @@ dependencies = [
  "web-sys",
 ]
 
+[[package]]
+name = "wide"
+version = "0.7.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce5da8ecb62bcd8ec8b7ea19f69a51275e91299be594ea5cc6ef7819e16cd03"
+dependencies = [
+ "bytemuck",
+ "safe_arch",
+]
+
 [[package]]
 name = "widestring"
 version = "1.2.1"