Add initial Wayland shell with clock and system tray

- Layer-shell bars drawn in software with tiny-skia and fontdue
- Clock widget centered at the top of the screen
- System tray in a top-right notch, acting as the
  StatusNotifierWatcher, with icons and right-click menus
- Live-reloaded TOML config for colors
  (~/.config/pell/config.toml)
- devenv setup for the Rust toolchain and Wayland libraries
- README: config, tray behaviour and AI disclosure

devenv.lock

@@ -0,0 +1,65 @@
+{
+  "nodes": {
+    "devenv": {
+      "locked": {
+        "dir": "src/modules",
+        "lastModified": 1790701375,
+        "narHash": "sha256-0FpLHIRDYiyo3EMTnMQSobZQknZaa3JuWo6vmMCK76o=",
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "fe20b5cba7ab5e93ae73f956a8d3efc50e1753f4",
+        "type": "github"
+      },
+      "original": {
+        "dir": "src/modules",
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "inputs": {
+        "nixpkgs-src": "nixpkgs-src"
+      },
+      "locked": {
+        "lastModified": 1789506231,
+        "narHash": "sha256-vNkJbtmqyBfFhn/HnzQo4ROuoyYWuy/allqTfJb4kMY=",
+        "owner": "cachix",
+        "repo": "devenv-nixpkgs",
+        "rev": "c2f38fe7f9e04d9aadd354d380f2bd40531d9737",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "ref": "rolling",
+        "repo": "devenv-nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1789370336,
+        "narHash": "sha256-6RSEDHIWQtesQKWSu5qRai8L2h4KgCgMEfJHstW99G4=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c7def046b9a883d46974757852106483d741586f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}