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.

docs/superpowers/specs/2026-09-29-native-sql-execution-smoke-checklist.md

@@ -0,0 +1,63 @@
+# Smoke checklist — native MySQL execution (0.8.2)
+
+These flows cannot be automated on this machine: `RunEvent::Opened` only fires
+for a bundled `.app` registered with LaunchServices, and a real MySQL 8 restore
+needs a live server. Run every box before publishing a draft release.
+
+Build first (both scripts exist — `build` in `desktop/package.json`, the Tauri
+CLI via the `tauri` script in `desktop/package.json`):
+
+    bun run --filter gridline-desktop build
+    bun run --filter gridline-desktop tauri build
+
+## A. Association and OS open
+
+- [ ] The built `.app` appears under **Finder → right-click a `.sql` file → Open With**.
+- [ ] The previous default handler for `.sql` is **unchanged** (rank is Alternate).
+      Refresh LaunchServices if it is stale:
+      `/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -f /Applications/Gridline.app`
+- [ ] With Gridline **closed**, double-click a `.sql` file → the app launches with a
+      query tab named after the file, containing the file's text.
+- [ ] With Gridline **running**, open another `.sql` file → a second tab appears
+      (no second app instance, and no duplicate of the first tab).
+- [ ] Open the **same** file twice → the existing tab is focused; edits in it are NOT reset.
+- [ ] With **no connection open**, open a `.sql` file → Home is shown with a banner
+      naming the file; after connecting, the tab opens automatically and the banner clears.
+- [ ] Open a file larger than 5 MB → nothing opens and no freeze occurs (a file over
+      `MAX_SQL_FILE_BYTES` is rejected by the buffer and must be routed to Tools → Restore,
+      whose own cap is 100 MB).
+- [ ] Open a `.txt` file via Open With → Gridline ignores it (no tab, no error dialog).
+- [ ] The notarized `Gridline_0.8.2_*.dmg` still carries the association and still launches.
+
+## B. Cell decoding (issue #41)
+
+- [ ] Connect to a MySQL database and open a table with `INT`/`BIGINT` columns:
+      the primary key renders its values, **not** NULL.
+- [ ] Columns of type `DECIMAL`, `DATE`, `DATETIME`, `TIMESTAMP`, `FLOAT`, `TINYINT`,
+      `BIT` and `YEAR` all render values.
+- [ ] Run the reporter's exact statement and confirm the ids are values:
+      `SELECT id, uuid, first_name FROM users ORDER BY id;`
+- [ ] A `BIGINT` column renders as a string and a `DECIMAL` renders with its exact
+      digits (no float rounding).
+- [ ] A `VARCHAR` column still renders as before (no regression on the types that worked).
+
+## C. Native restore
+
+- [ ] Tools → Restore against a MySQL 8 server whose user authenticates with
+      `caching_sha2_password` (the case the bundled MariaDB client cannot reach):
+      the restore completes.
+- [ ] The MySQL restore form is usable even when no `mariadb`/`mysql` client is installed.
+- [ ] `clean` ON into a **non-empty** target: objects the dump defines are replaced;
+      an unrelated table created beforehand **survives**.
+- [ ] `clean` OFF into a non-empty target: fails with `table already exists`, and the
+      error names the statement position.
+- [ ] A dump containing a trigger or stored routine (with `DELIMITER`) restores without
+      a syntax error.
+- [ ] Cancel a long restore → it stops and reports cancellation rather than running to completion.
+- [ ] The form states that a failed MySQL restore cannot be rolled back.
+
+## D. Suite
+
+- [ ] `cd desktop/src-tauri && cargo test --lib` → 0 failures.
+- [ ] `cd desktop && bun run test` → 0 failures.
+- [ ] `cd desktop && bunx tsc --noEmit` → clean.