feat(init): scaffold cargo workspace and CI

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

crates/gui/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "log-viewer-gui"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+egui.workspace = true
+eframe.workspace = true
+log-viewer-core.workspace = true

crates/gui/src/main.rs

@@ -0,0 +1 @@
+fn main() {}