feat(m3): search and export

- Pidgin lexer: words, escaped phrases (strict closing), parens
- Full-Pidgin token-level parser, strict: malformed input throws
  SearchSyntaxException (BREAKING: lenient degradation removed from
  the plan; M7 must surface the error, M8 USAGE.md documents strict
  behavior)
- AST with reference-equality collection terms; structural
  comparison lives in the test-side SearchNodeComparer (YYC MARK
  note records the record-equality pitfall)
- SQL compiler: parameterized predicate over cards alias, LIKE
  escaping, COLLATE NOCASE exact matches, tag EXISTS / column IN
  subqueries
- Markdown exporter: ResX-driven templates, per-language export
  time AND card time patterns, kebab i18n file names, table cell
  escaping
- New RgbColor value type (byte components, strict #RRGGBB parse,
  canonical lowercase text) wired through TagModel and repository
- 57 new tests (grammar branches, strict errors, SQL end-to-end,
  en/zh export snapshots, color conversions)

YKanBan.Tests/Export/MarkdownExporterTests.cs

@@ -0,0 +1,171 @@
+using System.Globalization;
+using YKanBan.Export;
+using YKanBan.Models;
+
+namespace YKanBan.Tests.Export;
+
+/// <summary>
+/// Tests for the Markdown exporter. Mutates the global Resources.Culture,
+/// therefore marked DoNotParallelize. Asserts real localized output for
+/// both supported languages.
+/// </summary>
+[TestClass]
+[DoNotParallelize]
+public class MarkdownExporterTests
+{
+    private static readonly DateTimeOffset ExportedAt = new(2026, 9, 30, 14, 25, 37, TimeSpan.Zero);
+
+    /// <summary>A local wall-clock moment, matching the exporter's conversion path.</summary>
+    private static DateTimeOffset Local(int year, int month, int day, int hour, int minute) =>
+        new DateTimeOffset(new DateTime(year, month, day, hour, minute, 0)).ToLocalTime();
+
+    /// <summary>Unix seconds for a local wall-clock time.</summary>
+    private static long UnixTimeOf(int year, int month, int day, int hour, int minute) =>
+        Local(year, month, day, hour, minute).ToUnixTimeSeconds();
+
+    /// <summary>Builds the board fixture: one working column with two cards, one empty column, two tags.</summary>
+    private static (IReadOnlyList<ColumnModel> Columns, IReadOnlyList<CardModel> Cards, IReadOnlyList<(TagModel, long)> Tags) CreateBoard()
+    {
+        long created = UnixTimeOf(2026, 9, 1, 10, 0);
+        long updated = UnixTimeOf(2026, 9, 28, 18, 30);
+
+        var columns = new List<ColumnModel>
+        {
+            new(1, "In Progress", "The work column", 100, 100),
+            new(2, "Empty", string.Empty, 100, 100),
+        };
+        var bug = new TagModel(1, "bug", RgbColor.Parse("#ff0000"), string.Empty);
+        var ui = new TagModel(2, "ui", RgbColor.Parse("#00ff00"), "Interface work");
+        var cards = new List<CardModel>
+        {
+            new(61, 1, "Fix login", "Body text", created, updated, [bug, ui]),
+            new(62, 1, string.Empty, string.Empty, created, updated, []),
+        };
+        var tags = new List<(TagModel, long)> { (bug, 1), (ui, 1) };
+        return (columns, cards, tags);
+    }
+
+    private static string Export(CultureInfo culture)
+    {
+        CultureInfo? original = Resources.Culture;
+        try
+        {
+            Resources.Culture = culture;
+            (IReadOnlyList<ColumnModel> columns, IReadOnlyList<CardModel> cards, IReadOnlyList<(TagModel, long)> tags) = CreateBoard();
+            return MarkdownExporter.Export("MyRepo", columns, cards, tags, ExportedAt);
+        }
+        finally
+        {
+            Resources.Culture = original;
+        }
+    }
+
+    private static string Normalize(string text) => text.Replace("\r\n", "\n");
+
+    [TestMethod]
+    public void EnglishOutputMatchesTemplate()
+    {
+        string created = Local(2026, 9, 1, 10, 0).ToString("yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);
+        string updated = Local(2026, 9, 28, 18, 30).ToString("yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);
+
+        string expected = Normalize($"""
+            # MyRepo
+            > Exported at: 2026-09-30 14:25:37
+
+            ## Column: In Progress (2)
+            The work column
+
+            ### #61 Fix login
+            Body text
+            - Tags: `bug` `ui`
+            - Created: {created}  Modified: {updated}
+
+            ### #62
+            - Created: {created}  Modified: {updated}
+
+            ## Column: Empty (0)
+
+            ## Tags
+            | Name | Color | Description | Usage |
+            |---|---|---|---|
+            | bug | #ff0000 |  | 1 |
+            | ui | #00ff00 | Interface work | 1 |
+            """);
+
+        Assert.AreEqual(expected + "\n", Normalize(Export(new CultureInfo("en"))));
+    }
+
+    [TestMethod]
+    public void ChineseOutputMatchesTemplate()
+    {
+        var chinese = new CultureInfo("zh-Hans");
+        string created = Local(2026, 9, 1, 10, 0).ToString("yyyy年M月d日 HH:mm", chinese);
+        string updated = Local(2026, 9, 28, 18, 30).ToString("yyyy年M月d日 HH:mm", chinese);
+
+        string expected = Normalize($"""
+            # MyRepo
+            > 导出时间：2026年9月30日 14:25
+
+            ## 列：In Progress（2）
+            The work column
+
+            ### #61 Fix login
+            Body text
+            - 标签：`bug` `ui`
+            - 创建：{created}　修改：{updated}
+
+            ### #62
+            - 创建：{created}　修改：{updated}
+
+            ## 列：Empty（0）
+
+            ## 标签总表
+            | 名称 | 颜色 | 描述 | 使用数 |
+            |---|---|---|---|
+            | bug | #ff0000 |  | 1 |
+            | ui | #00ff00 | Interface work | 1 |
+            """);
+
+        Assert.AreEqual(expected + "\n", Normalize(Export(new CultureInfo("zh-Hans"))));
+    }
+
+    [TestMethod]
+    public void FileNameFollowsLanguage()
+    {
+        CultureInfo? original = Resources.Culture;
+        try
+        {
+            Resources.Culture = new CultureInfo("en");
+            Assert.AreEqual("MyRepo-export-20260930-142537.md", MarkdownExporter.BuildFileName("MyRepo", ExportedAt));
+
+            Resources.Culture = new CultureInfo("zh-Hans");
+            Assert.AreEqual("MyRepo-导出-20260930-142537.md", MarkdownExporter.BuildFileName("MyRepo", ExportedAt));
+        }
+        finally
+        {
+            Resources.Culture = original;
+        }
+    }
+
+    [TestMethod]
+    public void TagTableCellsEscapePipesAndLineBreaks()
+    {
+        CultureInfo? original = Resources.Culture;
+        try
+        {
+            Resources.Culture = new CultureInfo("en");
+            var tag = new TagModel(1, "a|b", RgbColor.Parse("#112233"), "first\nsecond");
+            string markdown = MarkdownExporter.Export("W",
+                [new ColumnModel(1, "C", string.Empty, 1, 1)],
+                [],
+                [(tag, 0L)],
+                ExportedAt);
+
+            StringAssert.Contains(markdown, "| a\\|b | #112233 | first second | 0 |");
+        }
+        finally
+        {
+            Resources.Culture = original;
+        }
+    }
+}