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/deck.rs

@@ -2,6 +2,7 @@
 
 use std::path::Path;
 
+use modelcraft_io::roots::Access;
 use serde_json::{Value, json};
 
 use super::req;
@@ -22,10 +23,10 @@ fn write(s: &mut Session, p: &Value) -> Result<Value> {
         let known: Vec<&str> = modelcraft_decks::FORMATS.iter().map(|f| f.name).collect();
         EngineError::Params(format!("unknown deck format `{shown}`; known: {}", known.join(", ")))
     })?;
-    let path = super::path_param(p, "path")?;
+    let path = super::file_param(s, p, "path", Access::Write)?;
     let steps: Option<Vec<String>> = super::opt(p, "steps")?;
     let deck = format.write_steps(&s.model, steps.as_deref())?;
-    modelcraft_io::fs::write_atomic(Path::new(path), deck.text.as_bytes(), false)?;
+    modelcraft_io::fs::write_atomic(Path::new(&path), deck.text.as_bytes(), false)?;
     Ok(json!({"format": format.name, "path": path, "bytes": deck.text.len(), "warnings": deck.warnings}))
 }