fix(begin): remove unused rel bindings and dead relationship label plumbing

Drops the unused `rel` variable bindings in `make_demo_sheet` and
removes the `relationships` field and `add_relationship` method from
`Labels`, which were never read by `to_graph_data` and caused dead-code
errors in the renderer-agnostic clippy run.

Also documents the two-invocation clippy requirement in CLAUDE.md so
the begin-crate check is not missed before a PR.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sean-parent

CLAUDE.md

@@ -27,8 +27,11 @@ cargo test --doc --workspace
 cargo test --workspace <test_name>
 
 # Lint (warnings are errors)
-cargo clippy --workspace -- -D warnings
-cargo clippy --fix --workspace
+# The begin crate is excluded from the workspace commands and checked separately
+# with --no-default-features to avoid platform-specific renderer dependencies.
+cargo clippy --workspace --exclude begin -- -D warnings
+cargo clippy -p begin --no-default-features -- -D warnings
+cargo clippy --fix --workspace --exclude begin
 
 # Docs
 cargo doc --lib --no-deps --open --workspace
@@ -53,8 +56,8 @@ git checkout -b <username>/<feature-name>
 
 Never commit directly to `main`.
 
-Before creating a PR, run the full check suite locally (fmt, clippy, and test from the
-Commands section above).
+Before creating a PR, run the full check suite locally — every command in the Commands
+section above, including both clippy invocations (workspace and begin).
 
 ## Project Status
 

begin/src/app.rs

@@ -23,7 +23,7 @@ pub fn make_demo_sheet() -> (Sheet, Labels) {
     let a = sheet.add_cell(2.0_f64);
     let b = sheet.add_cell(3.0_f64);
 
-    let rel = sheet
+    sheet
         .add_relationship(vec![
             Method::from_fn_2_1([a, b], c, |x: &f64, y: &f64| Ok(x * y)),
             Method::from_fn_2_1([b, c], a, |x: &f64, y: &f64| Ok(y / x)),
@@ -34,7 +34,7 @@ pub fn make_demo_sheet() -> (Sheet, Labels) {
     let d = sheet.add_cell(4.0_f64);
     let e = sheet.add_cell(5.0_f64);
 
-    let rel = sheet
+    sheet
         .add_relationship(vec![
             Method::from_fn_2_1([d, e], c, |x: &f64, y: &f64| Ok(x * y)),
             Method::from_fn_2_1([c, e], d, |x: &f64, y: &f64| Ok(x / y)),

begin/src/bridge.rs

@@ -4,8 +4,6 @@
 //! with stable [`CellId`] and [`RelationshipId`] keys. [`to_graph_data`] serializes a
 //! [`Sheet`] and its [`Labels`] into a [`GraphData`] value ready for JSON encoding.
 
-use std::collections::HashMap;
-
 use indexmap::IndexMap;
 use property_model::{CellId, Error, RelationshipId, Sheet};
 use serde::Serialize;
@@ -28,16 +26,13 @@ pub struct CellMeta {
 pub struct Labels {
     /// Cells in insertion order (preserves sidebar ordering).
     pub cells: IndexMap<CellId, CellMeta>,
-    /// Relationship labels (reserved for future tooltip display).
-    pub relationships: HashMap<RelationshipId, String>,
 }
 
 impl Labels {
     /// Creates an empty label set.
     pub fn new() -> Self {
         Self {
             cells: IndexMap::new(),
-            relationships: HashMap::new(),
         }
     }
 
@@ -69,13 +64,6 @@ impl Labels {
             },
         );
     }
-
-    /// Registers a label for a relationship.
-    ///
-    /// - Precondition: `id` is a live relationship in the sheet this `Labels` will be used with.
-    pub fn add_relationship(&mut self, id: RelationshipId, label: &str) {
-        self.relationships.insert(id, label.to_owned());
-    }
 }
 
 impl Default for Labels {
@@ -237,12 +225,11 @@ mod tests {
         let c = sheet.add_cell(0.0_f64);
         labels.add_cell::<f64>(c, "c");
 
-        let rel = sheet
+        sheet
             .add_relationship(vec![Method::from_fn_2_1([a, b], c, |x: &f64, y: &f64| {
                 Ok(x * y)
             })])
             .unwrap();
-        labels.add_relationship(rel, "×");
 
         (sheet, labels)
     }
@@ -341,12 +328,11 @@ mod tests {
         let b = sheet.add_cell(3.0_f64);
         labels.add_cell::<f64>(b, "b");
 
-        let rel = sheet
+        sheet
             .add_relationship(vec![Method::from_fn_2_1([a, b], c, |x: &f64, y: &f64| {
                 Ok(x * y)
             })])
             .unwrap();
-        labels.add_relationship(rel, "×");
 
         (sheet, labels)
     }