MCP server: modelcraft-cli mcp (headless or bridged), read/write roots, end-to-end analysis over MCP (#48)

* io: read and write roots that confine an automation client's file access

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* engine: every file a command reads or writes is checked against the session's roots

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* engine: headless pictures of a session (model, geometry, deformed shape and contours)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* mcp: MCP server over stdio with headless and connected backends, roots and caps

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* cli: modelcraft-cli mcp [--connect ADDR | --headless] with automation read and write roots

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* mcp: end-to-end analysis of a corpus part over MCP (open, tet mesh, define, solve, probe, render)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* docs: MCP server (docs/mcp.md), Claude Code setup, roots; architecture, README, roadmap, attribution

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/geometry.rs

@@ -3,6 +3,7 @@ use std::sync::Arc;
 use modelcraft_geometry::tagged_mesh;
 use modelcraft_geometry::{MAX_DESIGN_BYTES, Shape, SurfaceMesh, open_design};
 use modelcraft_io::SourceFile;
+use modelcraft_io::roots::Access;
 use serde_json::{Value, json};
 
 use crate::{CommandKind, CommandSpec, EngineError, Result, Session};
@@ -40,9 +41,9 @@ pub const IMPORT_MESH: CommandSpec = CommandSpec {
 };
 
 fn open(s: &mut Session, p: &Value) -> Result<Value> {
-    let path = super::path_param(p, "path")?;
-    let bytes = modelcraft_geometry::read_file(path, MAX_DESIGN_BYTES)?;
-    let source = SourceFile::of(super::file::absolute(path), &bytes)?;
+    let path = super::file_param(s, p, "path", Access::Read)?;
+    let bytes = modelcraft_geometry::read_file(&path, MAX_DESIGN_BYTES)?;
+    let source = SourceFile::of(super::file::absolute(&path), &bytes)?;
     let design = open_design(&bytes)?;
     let out = json!({
         "name": design.name,
@@ -96,12 +97,12 @@ fn tessellate(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn import_mesh(s: &mut Session, p: &Value) -> Result<Value> {
-    let path = super::path_param(p, "path")?;
+    let path = super::file_param(s, p, "path", Access::Read)?;
     if s.sources.meshes.len() >= modelcraft_io::MAX_MESH_SOURCES {
         return Err(EngineError::Params(format!("a model imports at most {} meshes", modelcraft_io::MAX_MESH_SOURCES)));
     }
-    let bytes = modelcraft_geometry::read_file(path, tagged_mesh::MAX_FILE_BYTES)?;
-    let source = SourceFile::of(super::file::absolute(path), &bytes)?;
+    let bytes = modelcraft_geometry::read_file(&path, tagged_mesh::MAX_FILE_BYTES)?;
+    let source = SourceFile::of(super::file::absolute(&path), &bytes)?;
     let surfaces = tagged_mesh::read_3mf(&bytes)?;
     let first = s.surfaces.len();
     let added: Vec<Value> = surfaces