feat(rpc): expose snapshot, compare and restore for request versions

Three commands, all host-independent so the browser build answers them from
the same model layer as the desktop:

- models_snapshot_request, for the edit-session boundaries only the frontend
  can see. It takes a reason and nothing else — the caller does not decide
  whether anything changed, because content addressing already has.
- models_request_version, which returns a version and the live request's
  content together so they are guaranteed comparable, plus the same
  content-hash verdict the backend uses rather than a second opinion formed in
  TypeScript.
- models_restore_request_version.

The browser host also snapshots before its own send, since its send pipeline
is in TypeScript rather than in the shared crate.

Bindings regenerated with CI's `cargo test --all --features
yaak-app-client/wry`, which also drops a stale ImportSourceResource from the
rpc-schema copy and adds a missing ImportSource to the plugins copy.

crates/yaak-models/bindings/gen_models.ts

@@ -139,6 +139,10 @@ export type GrpcConnection = {
   state: GrpcConnectionState;
   trailers: { [key in string]?: string };
   url: string;
+  /**
+   * The request version this connection was opened from, when one was captured.
+   */
+  versionId: string | null;
 };
 
 export type GrpcConnectionState = "initialized" | "connected" | "closed";
@@ -243,6 +247,10 @@ export type HttpResponse = {
   state: HttpResponseState;
   url: string;
   version: string | null;
+  /**
+   * The request version this response was sent from, when one was captured.
+   */
+  versionId: string | null;
 };
 
 export type HttpResponseEvent = {
@@ -382,6 +390,28 @@ export type ModelPayload = {
   change: ModelChangeEvent;
 };
 
+export type ModelVersion = {
+  model: "model_version";
+  id: string;
+  createdAt: string;
+  updatedAt: string;
+  workspaceId: string;
+  /**
+   * The `model` field of the versioned model, eg. `http_request`.
+   */
+  modelType: string;
+  modelId: string;
+  contentHash: string;
+  document: Record<string, any>;
+  reason: ModelVersionReason;
+};
+
+/**
+ * Why a version was captured. Not a UI label — the frontend decides how to
+ * phrase these — but it is what makes a history readable when debugging.
+ */
+export type ModelVersionReason = "send" | "switch" | "idle" | "restore" | "manual";
+
 export type ParentAuthentication = {
   authentication: Record<string, any>;
   authenticationType: string | null;
@@ -425,6 +455,23 @@ export type ProxySetting =
 
 export type ProxySettingAuth = { user: string; password: string };
 
+/**
+ * One version, next to the request as it stands now.
+ *
+ * Both halves come from the same place so they are guaranteed comparable: the
+ * frontend renders them side by side, and `differs` is the same content-hash
+ * comparison the backend uses everywhere else rather than a second opinion
+ * formed in TypeScript.
+ */
+export type RequestVersionComparison = {
+  version: ModelVersion;
+  /**
+   * The live request's editable content, in the same shape as the version's document.
+   */
+  currentDocument: Record<string, any>;
+  differs: boolean;
+};
+
 export type Settings = {
   model: "settings";
   id: string;
@@ -488,6 +535,10 @@ export type WebsocketConnection = {
   state: WebsocketConnectionState;
   status: number;
   url: string;
+  /**
+   * The request version this connection was opened from, when one was captured.
+   */
+  versionId: string | null;
 };
 
 export type WebsocketConnectionState = "initialized" | "connected" | "closing" | "closed";

crates/yaak-models/src/models.rs

@@ -3285,6 +3285,23 @@ impl UpsertModelInfo for ModelVersion {
     }
 }
 
+/// One version, next to the request as it stands now.
+///
+/// Both halves come from the same place so they are guaranteed comparable: the
+/// frontend renders them side by side, and `differs` is the same content-hash
+/// comparison the backend uses everywhere else rather than a second opinion
+/// formed in TypeScript.
+#[derive(Debug, Clone, Serialize, Deserialize, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export, export_to = "gen_models.ts")]
+pub struct RequestVersionComparison {
+    pub version: ModelVersion,
+    /// The live request's editable content, in the same shape as the version's document.
+    #[ts(type = "Record<string, any>")]
+    pub current_document: Value,
+    pub differs: bool,
+}
+
 /// Only used as a `from_row` fallback for an unparseable settings column. The
 /// value a *new* model gets comes from that model's `Default` impl.
 fn default_request_message_size_setting() -> InheritedIntSetting {

crates/yaak-models/src/versions.rs

@@ -33,13 +33,46 @@ pub fn version_document<T: Serialize>(model: &T) -> Result<Value> {
 }
 
 /// The hash a version is addressed by.
-///
-/// Canonical by construction: `serde_json::Map` is a `BTreeMap` here, so
-/// serialization already visits keys in sorted order and two documents that
-/// differ only in key order hash the same.
 pub fn content_hash(document: &Value) -> Result<String> {
-    let canonical = serde_json::to_vec(document)?;
-    Ok(hex::encode(Sha256::digest(&canonical)))
+    let mut canonical = String::new();
+    write_canonical(document, &mut canonical);
+    Ok(hex::encode(Sha256::digest(canonical.as_bytes())))
+}
+
+/// Serialize with object keys in sorted order.
+///
+/// Plain `to_string` would not do: whether `serde_json::Map` preserves
+/// insertion order or sorts is a workspace-wide feature decision, and a
+/// document read back from SQLite has whatever order it was written in. Sorting
+/// here makes the hash depend on the content and nothing else, in every build.
+fn write_canonical(value: &Value, out: &mut String) {
+    match value {
+        Value::Object(map) => {
+            let mut keys = map.keys().collect::<Vec<_>>();
+            keys.sort_unstable();
+            out.push('{');
+            for (i, key) in keys.into_iter().enumerate() {
+                if i > 0 {
+                    out.push(',');
+                }
+                write_canonical(&Value::String(key.clone()), out);
+                out.push(':');
+                write_canonical(&map[key], out);
+            }
+            out.push('}');
+        }
+        Value::Array(items) => {
+            out.push('[');
+            for (i, item) in items.iter().enumerate() {
+                if i > 0 {
+                    out.push(',');
+                }
+                write_canonical(item, out);
+            }
+            out.push(']');
+        }
+        scalar => out.push_str(&scalar.to_string()),
+    }
 }
 
 /// Lay a version's document back over a live model.
@@ -142,8 +175,10 @@ mod tests {
         );
     }
 
-    /// The hash has to survive being written to and read back from the
-    /// database, which does not preserve key order.
+    /// The hash has to survive a round trip through SQLite, which stores the
+    /// document as text and hands back whatever order it was written in. It
+    /// also has to survive `serde_json`'s `preserve_order` feature being on in
+    /// one build of the workspace and off in another.
     #[test]
     fn key_order_does_not_change_the_hash() {
         let a: Value = serde_json::from_str(r#"{"url":"a","method":"GET"}"#).unwrap();
@@ -151,6 +186,25 @@ mod tests {
         assert_eq!(content_hash(&a).unwrap(), content_hash(&b).unwrap());
     }
 
+    #[test]
+    fn key_order_does_not_change_the_hash_when_nested() {
+        let a: Value =
+            serde_json::from_str(r#"{"body":{"text":"x","type":"json"},"headers":[{"a":1,"b":2}]}"#)
+                .unwrap();
+        let b: Value =
+            serde_json::from_str(r#"{"headers":[{"b":2,"a":1}],"body":{"type":"json","text":"x"}}"#)
+                .unwrap();
+        assert_eq!(content_hash(&a).unwrap(), content_hash(&b).unwrap());
+    }
+
+    /// Sorting keys must not make different documents collide.
+    #[test]
+    fn array_order_still_changes_the_hash() {
+        let a: Value = serde_json::from_str(r#"{"headers":[{"n":"a"},{"n":"b"}]}"#).unwrap();
+        let b: Value = serde_json::from_str(r#"{"headers":[{"n":"b"},{"n":"a"}]}"#).unwrap();
+        assert_ne!(content_hash(&a).unwrap(), content_hash(&b).unwrap());
+    }
+
     #[test]
     fn applying_a_document_keeps_the_live_model_identity() {
         let live = serde_json::to_value(request()).unwrap();