feat(cli): add hydrate stage restore

src/cli.rs

@@ -474,6 +474,12 @@ pub enum StageAction {
     /// what it discarded first, and parks a recoverable copy in
     /// `.hydrate/stage.discarded.json`. Purely local: no network call.
     Discard,
+
+    /// Put back the stage `discard` most recently parked. Refuses if the
+    /// current stage is not empty (commit or discard it first) or if the
+    /// recovery slot was parked from a different branch than the one now
+    /// bound. Purely local: no network call. Consumes the recovery file.
+    Restore,
 }
 
 #[derive(Debug, Subcommand)]

src/cmd/guide.rs

@@ -76,6 +76,9 @@ Editing in place
   hydrate stage discard        throw away everything staged (local; keeps a
                                recoverable copy). NOT the same as `clear`, which
                                stages deletions rather than undoing your edits
+  hydrate stage restore        put back the stage the last discard parked;
+                               refuses over a non-empty stage or onto a
+                               different branch than the one it was parked from
 
 Choosing a project
   Commands resolve the project from --project <name|id>, else the HYD_PROJECT
@@ -162,6 +165,30 @@ mod tests {
         }
     }
 
+    #[test]
+    fn guide_documents_stage_restore_and_its_two_refusals() {
+        // `discard` promised recoverability from `.hydrate/stage.discarded.json`
+        // but nothing read it back — `restore` is what makes that true. Pin
+        // both places the guide claims a mistake is recoverable so the two
+        // verbs cannot drift apart.
+        assert!(
+            GUIDE.contains("hydrate stage restore"),
+            "guide never mentions `stage restore`"
+        );
+        let start = GUIDE
+            .find("hydrate stage restore")
+            .expect("stage restore line");
+        let line = &GUIDE[start..];
+        assert!(
+            line.contains("non-empty stage") || line.contains("refuses"),
+            "guide does not say restore refuses over live work: {line}"
+        );
+        assert!(
+            line.contains("different branch"),
+            "guide does not say restore refuses across branches: {line}"
+        );
+    }
+
     #[test]
     fn guide_does_not_restate_retired_rules() {
         // The guide is the agent onboarding surface, so a stale rule here

src/cmd/mod.rs

@@ -64,6 +64,7 @@ pub fn dispatch(cli: Cli) -> ExitCode {
         },
         Command::Stage { action } => match action {
             StageAction::Discard => finish(stage::discard(mode), mode),
+            StageAction::Restore => finish(stage::restore(mode), mode),
         },
         Command::Status => finish(status::run(mode), mode),
         Command::Diff => finish(diff::run(mode), mode),