feat: make column title and tag name uniqueness case-insensitive

YKanBan.Tests/Storage/Workspace/WorkspaceSchemaTests.cs

@@ -65,15 +65,44 @@ public class WorkspaceSchemaTests
     }
 
     [TestMethod]
-    public void ColumnTitlesCompareCaseSensitively()
+    public void ColumnTitlesDifferingOnlyInAsciiCaseAreRejected()
     {
         using var db = new FreshDatabase();
-        // BINARY collation: 'Foo' and 'foo' are distinct titles.
+        // NOCASE uniqueness: 'Foo' and 'foo' cannot coexist.
         SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('Foo', 1, 1);");
-        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('foo', 1, 1);");
+        Assert.ThrowsExactly<SqliteException>(() =>
+            SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('foo', 1, 1);"));
+    }
+
+    [TestMethod]
+    public void ColumnTitlesDifferingOnlyInNonAsciiCaseAreAccepted()
+    {
+        using var db = new FreshDatabase();
+        // NOCASE folds ASCII only: 'Ä' and 'ä' remain distinct titles.
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('Ä', 1, 1);");
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('ä', 1, 1);");
         Assert.AreEqual(2L, SqliteTestHelper.ScalarLong(db.Connection, "SELECT COUNT(*) FROM columns;"));
     }
 
+    [TestMethod]
+    public void ColumnTitleCaseOnlyRenameOfSameRowIsAccepted()
+    {
+        using var db = new FreshDatabase();
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('Foo', 1, 1);");
+        int affected = SqliteTestHelper.Exec(db.Connection, "UPDATE columns SET title = 'foo' WHERE id = 1;");
+        Assert.AreEqual(1, affected);
+    }
+
+    [TestMethod]
+    public void ColumnTitlesStillOrderByCodePoint()
+    {
+        using var db = new FreshDatabase();
+        // Uniqueness is NOCASE, but the column collation stays BINARY: 'B' (0x42) sorts before 'a' (0x61).
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('a', 1, 1);");
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO columns (title, created_at, updated_at) VALUES ('B', 1, 1);");
+        Assert.AreEqual("B", SqliteTestHelper.ScalarString(db.Connection, "SELECT title FROM columns ORDER BY title LIMIT 1;"));
+    }
+
     [TestMethod]
     public void EmptyTagNameIsRejected()
     {
@@ -103,6 +132,24 @@ public class WorkspaceSchemaTests
             SqliteTestHelper.Exec(db.Connection, "INSERT INTO tags (name, color) VALUES ('bug', '#445566');"));
     }
 
+    [TestMethod]
+    public void TagNamesDifferingOnlyInAsciiCaseAreRejected()
+    {
+        using var db = new FreshDatabase();
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO tags (name, color) VALUES ('bug', '#112233');");
+        Assert.ThrowsExactly<SqliteException>(() =>
+            SqliteTestHelper.Exec(db.Connection, "INSERT INTO tags (name, color) VALUES ('BUG', '#445566');"));
+    }
+
+    [TestMethod]
+    public void TagNamesDifferingOnlyInNonAsciiCaseAreAccepted()
+    {
+        using var db = new FreshDatabase();
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO tags (name, color) VALUES ('Ä', '#112233');");
+        SqliteTestHelper.Exec(db.Connection, "INSERT INTO tags (name, color) VALUES ('ä', '#445566');");
+        Assert.AreEqual(2L, SqliteTestHelper.ScalarLong(db.Connection, "SELECT COUNT(*) FROM tags;"));
+    }
+
     [TestMethod]
     [DataRow("#000000")]
     [DataRow("#FFFFFF")]

YKanBan/Storage/Workspace/WorkspaceSchema.cs

@@ -6,6 +6,11 @@ namespace YKanBan.Storage.Workspace;
 /// assignments. Data validity is expressed in DDL (CHECK / UNIQUE / FOREIGN
 /// KEY) so every stored row is valid by construction, and cascading deletes
 /// are covered by the same DDL.
+///
+/// Title and name uniqueness is NOCASE (ASCII case folding) while the columns
+/// themselves keep the default BINARY collation, so ordering by title stays
+/// code-point based. Until the first release the v1 script may be edited in
+/// place; after it, every schema change must be appended as a new migration.
 /// </summary>
 public static class WorkspaceSchema
 {
@@ -22,10 +27,11 @@ public static class WorkspaceSchema
         new SchemaMigration(CurrentVersion, "initial schema", """
             CREATE TABLE columns (
                 id          INTEGER PRIMARY KEY AUTOINCREMENT,
-                title       TEXT    NOT NULL UNIQUE CHECK (length(title) > 0),
+                title       TEXT    NOT NULL CHECK (length(title) > 0),
                 description TEXT    NOT NULL DEFAULT '',
                 created_at  INTEGER NOT NULL,
-                updated_at  INTEGER NOT NULL
+                updated_at  INTEGER NOT NULL,
+                UNIQUE (title COLLATE NOCASE)
             );
 
             CREATE TABLE cards (
@@ -39,9 +45,10 @@ public static class WorkspaceSchema
 
             CREATE TABLE tags (
                 id          INTEGER PRIMARY KEY AUTOINCREMENT,
-                name        TEXT    NOT NULL UNIQUE CHECK (length(name) > 0),
+                name        TEXT    NOT NULL CHECK (length(name) > 0),
                 color       TEXT    NOT NULL CHECK (color GLOB '#[0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f]'),
-                description TEXT    NOT NULL DEFAULT ''
+                description TEXT    NOT NULL DEFAULT '',
+                UNIQUE (name COLLATE NOCASE)
             );
 
             CREATE TABLE card_tags (

docs/PLAN.md

@@ -57,18 +57,20 @@
 
 ```
 columns: id INTEGER PK AUTOINCREMENT,
-         title TEXT NOT NULL UNIQUE COLLATE NOCASE CHECK (length(title) > 0),
+         title TEXT NOT NULL CHECK (length(title) > 0),
          description TEXT NOT NULL DEFAULT '',
-         created_at INT NOT NULL, updated_at INT NOT NULL
+         created_at INT NOT NULL, updated_at INT NOT NULL,
+         UNIQUE (title COLLATE NOCASE)      ← 仅唯一性 NOCASE，列本身保持 BINARY（排序按码点）
 cards:   id INTEGER PK AUTOINCREMENT,
          column_id INT NOT NULL → columns.id ON DELETE CASCADE,
          title TEXT NOT NULL DEFAULT '',
          content TEXT NOT NULL DEFAULT '',
          created_at INT NOT NULL, updated_at INT NOT NULL
 tags:    id INTEGER PK AUTOINCREMENT,
-         name TEXT NOT NULL UNIQUE COLLATE NOCASE CHECK (length(name) > 0),
+         name TEXT NOT NULL CHECK (length(name) > 0),
          color TEXT NOT NULL CHECK (GLOB '#'+六位十六进制，即 #RRGGBB 形态),
-         description TEXT NOT NULL DEFAULT ''
+         description TEXT NOT NULL DEFAULT '',
+         UNIQUE (name COLLATE NOCASE)
 card_tags: (card_id, tag_id) 复合主键，双向 ON DELETE CASCADE
 ```