chore: drop design-section cross-refs from core comments

Keep module docs self-describing without pointing at DESIGN §N.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/vnidrop/src/device_relationship/crypto.rs

@@ -1,4 +1,4 @@
-//! Relationship-grant possession proofs (design §7).
+//! Relationship-grant possession proofs.
 
 use crate::{
     error::VnidropError,

crates/vnidrop/src/device_relationship/lifecycle.rs

@@ -1,4 +1,4 @@
-//! Forget, block, grant rotation, and minimal revocation tombstones (design §7–§8).
+//! Forget, block, grant rotation, and minimal revocation tombstones.
 
 use serde_json::json;
 

crates/vnidrop/src/device_relationship/mod.rs

@@ -1,7 +1,7 @@
 //! Experimental saved-device mutual-consent relationships.
 //!
-//! Implements design §6/§7: pending outgoing/incoming states, directional grants
-//! bound to relationship generation, and Saved only after mutual acknowledgement.
+//! Pending outgoing/incoming states, directional grants bound to relationship
+//! generation, and Saved only after mutual acknowledgement.
 
 mod crypto;
 mod lifecycle;

crates/vnidrop/src/device_relationship/service.rs

@@ -875,7 +875,7 @@ impl DeviceRelationshipService {
             )));
         }
         // Established relationships record a protocol floor and reject silent
-        // downgrade attempts (design §7 / §15).
+        // downgrade attempts.
         if protocol_version < row.minimum_protocol_version {
             return Err(VnidropError::protocol_incompatible(anyhow::anyhow!(
                 "relationship protocol downgrade is forbidden"