fix(dev): resolve stale editable packages together

tools/repo/sync-python-environment.py

@@ -236,7 +236,7 @@ def build_install_plan(
     removed_paths = set(previous_inputs) - set(current_inputs)
     stale_requirements = requirements_key in changed_paths or requirements_key in removed_paths
 
-    commands: list[tuple[str, ...]] = []
+    installs: list[tuple[str, ...]] = []
     warnings: list[str] = []
 
     if stale_requirements:
@@ -247,8 +247,7 @@ def build_install_plan(
                 "requirements changed in a way that needs the full resolver.",
                 (full_command,),
             )
-        for install_args in delta.commands:
-            commands.append((python, "-m", "pip", "install", *install_args))
+        installs.extend(delta.commands)
         warnings.extend(delta.warnings)
         changed_paths.discard(requirements_key)
         removed_paths.discard(requirements_key)
@@ -266,7 +265,7 @@ def build_install_plan(
                 f"tracked input changed outside a known local project: {path}",
                 (full_command,),
             )
-        commands.append((python, "-m", "pip", "install", *entry.install_args))
+        installs.append(entry.install_args)
 
     if removed_paths:
         return InstallPlan(
@@ -275,12 +274,19 @@ def build_install_plan(
             (full_command,),
         )
 
-    deduped_commands = tuple(dict.fromkeys(commands))
-    if deduped_commands:
+    deduped_installs = tuple(dict.fromkeys(installs))
+    if deduped_installs:
+        command = (
+            python,
+            "-m",
+            "pip",
+            "install",
+            *(argument for install_args in deduped_installs for argument in install_args),
+        )
         return InstallPlan(
             "Selective Python environment sync",
-            f"installing {len(deduped_commands)} stale local requirement(s).",
-            deduped_commands,
+            f"installing {len(deduped_installs)} stale local requirement(s) in one resolver transaction.",
+            (command,),
             tuple(warnings),
         )
     return InstallPlan(