GridSpaces: per-workspace n×m tiling for GNOME Shell 48

Mark a workspace as a grid; windows auto-fill cells, Alt+drag dividers to
resize rows/columns, drag-to-swap, overflow pops to a normal workspace.
Normal workspaces untouched. Tiling Assistant coexistence.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

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+# GridSpaces
+
+A GNOME Shell extension that turns a chosen workspace into a flexible tiling
+grid. Normal workspaces are left completely untouched.
+
+> **Status: experimental / alpha.** GNOME Shell 48, Wayland & X11.
+> Developed and tested inside a throwaway VM — a buggy shell extension can
+> crash your session on Wayland. Try it the same way (see *Safety* below).
+
+## What it does
+
+- Mark any workspace as a **grid workspace** from the panel button (⊞).
+- A grid workspace is a stack of **rows**; each row has its own column count.
+  Every cell holds at most one window, which is resized to fill the cell.
+- Any window entering a grid workspace auto-fills the first free cell.
+  When the grid is full, the window bounces back to where it came from.
+- **Drag a window onto another cell to swap** the two windows.
+- **Alt+drag the divider lines** to resize adjacent rows / columns. Sizes are
+  percentages of the work area and always sum to 100; a preview line follows
+  the pointer and the change is applied on release.
+- Removing a row / shrinking the grid pops the overflow windows to the
+  nearest normal workspace.
+- Coexists with Ubuntu's **Tiling Assistant**: its drop popup is suppressed
+  only while a grid workspace is active, and restored otherwise.
+
+## Install
+
+```sh
+git clone https://git.hangman-lab.top/hzhang/GridSpaces.git \
+  ~/.local/share/gnome-shell/extensions/gridspaces@hzhang.local
+```
+
+Then log out and back in (Wayland cannot hot-load a new extension), and:
+
+```sh
+gnome-extensions enable gridspaces@hzhang.local
+```
+
+## Usage
+
+1. Switch to the workspace you want to tile.
+2. Click the ⊞ panel button → toggle **Grid workspace** on.
+3. Use **Add row** and the per-row column steppers to shape the layout.
+4. **Alt+drag** the divider lines to adjust row heights / column widths.
+5. Open or drag windows in; drag a window onto another cell to swap.
+
+## Safety
+
+This is an in-development GNOME Shell extension. On a Wayland session an
+unhandled error in a shell extension can crash the whole session. **Do not
+add it to your autostart while iterating.** Test in a VM with a clean
+snapshot, or at minimum enable it manually (never via the autostart list) so
+a crash recovers to a clean desktop instead of a login loop.
+
+## License
+
+MIT