feat(mysql): native SQL execution — fix #41 type decoding, in-process restore, .sql open-with (#42)

Fixes #41.

MySQL columns now decode by their declared type instead of a blind try_get chain,
so every non-string type (integers, DECIMAL, BIT, YEAR, DATE/TIME/DATETIME/TIMESTAMP)
renders its value instead of NULL. MySQL restore runs in-process over the sqlx driver
(no bundled MariaDB client, so MySQL 8 caching_sha2_password works) and the Clean toggle
is implemented. .sql files can be opened with Gridline from the OS file manager.

Verified: cargo test --lib 442 passed / 0 failed; bun run test 133 files / 1151 tests
exit 0; tsc clean; both live MySQL 8 integration tests pass with the bundled CLI hidden.

desktop/src/stores/dbViewerStore.test.ts

@@ -638,3 +638,46 @@ describe("roles slice", () => {
     expect(useDbViewerStore.getState().tabs.filter((x) => x.form?.kind === "table").length).toBe(1);
   });
 });
+
+describe("openQueryTab with an initial script", () => {
+  it("seeds the tab text and label from the payload", () => {
+    useDbViewerStore.setState({ tabs: [], activeTabId: null });
+
+    useDbViewerStore.getState().openQueryTab({
+      sql: "SELECT 1;",
+      label: "student_db.sql",
+      filePath: "/Users/me/student_db.sql",
+    });
+
+    const tab = useDbViewerStore.getState().tabs.slice(-1)[0]!;
+    expect(tab.tabType).toBe("query");
+    expect(tab.query).toBe("SELECT 1;");
+    expect(tab.table).toBe("student_db.sql");
+    expect(tab.filePath).toBe("/Users/me/student_db.sql");
+  });
+
+  it("focuses an existing tab for the same file instead of duplicating it", () => {
+    useDbViewerStore.setState({ tabs: [], activeTabId: null });
+    const payload = {
+      sql: "SELECT 1;",
+      label: "student_db.sql",
+      filePath: "/Users/me/student_db.sql",
+    };
+    useDbViewerStore.getState().openQueryTab(payload);
+    useDbViewerStore.getState().openQueryTab({ ...payload, sql: "SELECT 2;" });
+
+    const queryTabs = useDbViewerStore.getState().tabs.filter((t) => t.tabType === "query");
+    expect(queryTabs).toHaveLength(1);
+    // The already-open tab keeps its text: re-opening must not clobber edits.
+    expect(queryTabs[0].query).toBe("SELECT 1;");
+  });
+
+  it("still opens a plain empty tab when called with no payload", () => {
+    useDbViewerStore.setState({ tabs: [], activeTabId: null });
+    useDbViewerStore.getState().openQueryTab();
+    const tab = useDbViewerStore.getState().tabs.slice(-1)[0]!;
+    expect(tab.tabType).toBe("query");
+    expect(tab.query).toBe("");
+    expect(tab.filePath).toBeUndefined();
+  });
+});