logiguard fork v2: patched GPUI on verified 8c74db0 tree

Rebuilt from the exact zed-industries/zed @ 8c74db00c4053d6c0a9037863d7bd048658da4ca
tree (previous orphan was based on a stale/wrong fetch). Same 3-file patch:
  - serial.rs: add SerialKind::KeyboardEnter
  - client.rs: store wl_keyboard.enter serial; add latest_serial_of()
  - window.rs: activate() uses keyboard-enter serial (Mutter focus gate)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/sum_tree/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+name = "sum_tree"
+version = "0.1.0"
+edition.workspace = true
+publish = false
+license = "Apache-2.0"
+description = "A sum tree data structure, a concurrency-friendly B-tree"
+
+[lints]
+workspace = true
+
+[lib]
+path = "src/sum_tree.rs"
+doctest = false
+
+[dependencies]
+heapless.workspace = true
+rayon.workspace = true
+log.workspace = true
+ztracing.workspace = true
+tracing.workspace = true
+proptest = { workspace = true, optional = true }
+
+[dev-dependencies]
+ctor.workspace = true
+rand.workspace = true
+proptest.workspace = true
+zlog.workspace = true
+
+
+[package.metadata.cargo-machete]
+ignored = ["tracing"]
+
+[features]
+test-support = ["proptest"]