cli/add_from_fs(feat[UX]): Improve output for many existing repositories

why: When scanning directories with many existing repos (37+), the output
was overwhelming and buried the important information about new repos.

what:
- Show summary only when >5 existing repos instead of full list
- Add clear "Found X new repositories to add:" section before confirmation
- Display new repos prominently with + prefix before asking to add
- Keep detailed output for ≤5 existing repos
- Add test for many existing repos scenario

This dramatically improves signal-to-noise ratio when adding repos to
large existing configurations.

refs: User feedback about 37-39 repo output drowning out 2 new additions

Author: tony

src/vcspull/cli/add_from_fs.py

@@ -239,18 +239,27 @@ def add_from_filesystem(
             repos_to_add.append((name, url, key))
 
     if existing_repos:
-        log.info(
-            f"{Fore.YELLOW}!{Style.RESET_ALL} Found "
-            f"{Fore.CYAN}{len(existing_repos)}{Style.RESET_ALL} "
-            f"existing repositories in configuration:"
-        )
-        for name, url, key in existing_repos:
+        # Show summary only when there are many existing repos
+        if len(existing_repos) > 5:
+            log.info(
+                f"{Fore.YELLOW}!{Style.RESET_ALL} Found "
+                f"{Fore.CYAN}{len(existing_repos)}{Style.RESET_ALL} "
+                f"existing repositories already in configuration."
+            )
+        else:
+            # Show details only for small numbers
             log.info(
-                f"  {Fore.BLUE}•{Style.RESET_ALL} {Fore.CYAN}{name}{Style.RESET_ALL} "
-                f"({Fore.YELLOW}{url}{Style.RESET_ALL}) at "
-                f"{Fore.MAGENTA}{key}{name}{Style.RESET_ALL} "
-                f"in {Fore.BLUE}{config_file_path}{Style.RESET_ALL}"
+                f"{Fore.YELLOW}!{Style.RESET_ALL} Found "
+                f"{Fore.CYAN}{len(existing_repos)}{Style.RESET_ALL} "
+                f"existing repositories in configuration:"
             )
+            for name, url, key in existing_repos:
+                log.info(
+                    f"  {Fore.BLUE}•{Style.RESET_ALL} {Fore.CYAN}{name}{Style.RESET_ALL} "
+                    f"({Fore.YELLOW}{url}{Style.RESET_ALL}) at "
+                    f"{Fore.MAGENTA}{key}{name}{Style.RESET_ALL} "
+                    f"in {Fore.BLUE}{config_file_path}{Style.RESET_ALL}"
+                )
 
     if not repos_to_add:
         if existing_repos:
@@ -260,9 +269,20 @@ def add_from_filesystem(
             )
         return
 
+    # Show what will be added
+    log.info(
+        f"\n{Fore.GREEN}Found {len(repos_to_add)} new "
+        f"{'repository' if len(repos_to_add) == 1 else 'repositories'} to add:{Style.RESET_ALL}"
+    )
+    for repo_name, repo_url, determined_base_key in repos_to_add:
+        log.info(
+            f"  {Fore.GREEN}+{Style.RESET_ALL} {Fore.CYAN}{repo_name}{Style.RESET_ALL} "
+            f"({Fore.YELLOW}{repo_url}{Style.RESET_ALL})"
+        )
+
     if not yes:
         confirm = input(
-            f"{Fore.CYAN}Add these repositories? [y/N]: {Style.RESET_ALL}"
+            f"\n{Fore.CYAN}Add these repositories? [y/N]: {Style.RESET_ALL}"
         ).lower()
         if confirm not in {"y", "yes"}:
             log.info(f"{Fore.RED}✗{Style.RESET_ALL} Aborted by user.")

tests/cli/test_add_from_fs.py

@@ -582,3 +582,67 @@ def test_mixed_existing_and_new_repos(
             assert f"Adding '{repo_name}' ({remote_url})" in caplog.text
 
         assert "Successfully updated" in caplog.text
+
+    def test_many_existing_repos_summary(
+        self,
+        create_git_remote_repo: CreateRepoPytestFixtureFn,
+        tmp_path: pathlib.Path,
+        git_commit_envvars: dict[str, str],
+        caplog: LogCaptureFixture,
+    ) -> None:
+        """Test that many existing repos show summary instead of full list."""
+        caplog.set_level("INFO")
+
+        # Create scan directory
+        scan_dir = tmp_path / "many_repos"
+        scan_dir.mkdir()
+
+        # Create many existing repos (more than 5)
+        existing_repo_data = []
+        for i in range(8):
+            repo_name = f"existing{i}"
+            remote_path = create_git_remote_repo()
+            remote_url = f"file://{remote_path}"
+            local_repo_path = scan_dir / repo_name
+
+            subprocess.run(
+                ["git", "clone", remote_url, str(local_repo_path)],
+                check=True,
+                capture_output=True,
+                env=git_commit_envvars,
+            )
+            existing_repo_data.append((repo_name, remote_url))
+
+        # Create one new repo
+        new_remote = create_git_remote_repo()
+        new_url = f"file://{new_remote}"
+        subprocess.run(
+            ["git", "clone", new_url, str(scan_dir / "new_repo")],
+            check=True,
+            capture_output=True,
+            env=git_commit_envvars,
+        )
+
+        # Pre-create config with existing repos
+        config_file = tmp_path / ".vcspull.yaml"
+        config_data = {str(scan_dir) + "/": dict(existing_repo_data)}
+        save_config_yaml(config_file, config_data)
+
+        # Run add_from_filesystem
+        add_from_filesystem(
+            scan_dir_str=str(scan_dir),
+            config_file_path_str=str(config_file),
+            recursive=True,
+            base_dir_key_arg=None,
+            yes=True,
+        )
+
+        # Verify summary message for many repos
+        assert "Found 8 existing repositories already in configuration." in caplog.text
+        # Should NOT list individual repos
+        assert "• existing0" not in caplog.text
+        assert "• existing7" not in caplog.text
+        
+        # Verify new repo is shown clearly
+        assert "Found 1 new repository to add:" in caplog.text
+        assert "+ new_repo" in caplog.text