Add zip upload and mapped-path picker for outline import

Sandbox source paths under a configured Imports:RootPath, browse it
from the web dialog, upload a zip that extracts into staging, and
import a single markdown file (agent infers chapter vs character).

tests/Novelly.Api.Tests/ImportBrowseServiceTests.cs

@@ -0,0 +1,100 @@
+using Microsoft.Extensions.Options;
+using Novelly.Api.Imports;
+
+namespace Novelly.Api.Tests;
+
+[TestFixture]
+public class ImportBrowseServiceTests
+{
+    private string _root = null!;
+    private ImportBrowseService _browse = null!;
+
+    [SetUp]
+    public void SetUp()
+    {
+        _root = Directory.CreateTempSubdirectory("novelly-browse-test-").FullName;
+        _browse = new ImportBrowseService(
+            Options.Create(new ImportOptions { RootPath = _root }),
+            new CapturingLogger<ImportBrowseService>());
+    }
+
+    [TearDown]
+    public void TearDown()
+    {
+        if (Directory.Exists(_root))
+        {
+            Directory.Delete(_root, recursive: true);
+        }
+    }
+
+    [Test]
+    public void Listing_the_root_returns_directories_before_files_ordered_by_name()
+    {
+        File.WriteAllText(Path.Combine(_root, "notes.md"), "# Notes");
+        Directory.CreateDirectory(Path.Combine(_root, "zeta"));
+        Directory.CreateDirectory(Path.Combine(_root, "alpha"));
+
+        var listing = _browse.List(null);
+
+        Assert.That(listing.Entries.Select(e => e.Name), Is.EqualTo(new[] { "alpha", "zeta", "notes.md" }));
+    }
+
+    [Test]
+    public void A_folder_with_an_outline_file_is_flagged_importable()
+    {
+        var folder = Path.Combine(_root, "my-novel");
+        Directory.CreateDirectory(folder);
+        File.WriteAllText(Path.Combine(folder, "outline.md"), "# My Novel");
+
+        var listing = _browse.List(null);
+
+        Assert.That(listing.Entries.Single(e => e.Name == "my-novel").LooksImportable, Is.True);
+    }
+
+    [Test]
+    public void An_empty_folder_is_not_flagged_importable()
+    {
+        Directory.CreateDirectory(Path.Combine(_root, "empty"));
+
+        var listing = _browse.List(null);
+
+        Assert.That(listing.Entries.Single(e => e.Name == "empty").LooksImportable, Is.False);
+    }
+
+    [Test]
+    public void The_staging_folder_is_hidden_from_listings()
+    {
+        Directory.CreateDirectory(Path.Combine(_root, ".novelly-staging"));
+        Directory.CreateDirectory(Path.Combine(_root, "visible"));
+
+        var listing = _browse.List(null);
+
+        Assert.That(listing.Entries.Select(e => e.Name), Is.EqualTo(new[] { "visible" }));
+    }
+
+    [Test]
+    public void Escaping_the_import_root_is_rejected()
+    {
+        Assert.That(() => _browse.List(".."), Throws.TypeOf<ArgumentException>());
+    }
+
+    [Test]
+    public void Browsing_without_a_configured_root_fails()
+    {
+        var unconfigured = new ImportBrowseService(
+            Options.Create(new ImportOptions()),
+            new CapturingLogger<ImportBrowseService>());
+
+        Assert.That(() => unconfigured.List(null), Throws.TypeOf<InvalidOperationException>());
+    }
+
+    [Test]
+    public void Listing_a_subfolder_reports_its_parent()
+    {
+        Directory.CreateDirectory(Path.Combine(_root, "child"));
+
+        var listing = _browse.List("child");
+
+        Assert.That(listing.ParentRelativePath, Is.EqualTo(""));
+    }
+}