feat(openpencil-app): skeleton crate (Stage F entry placeholder)

crates/openpencil-app/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "openpencil-app"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+description = "OpenPencil entry point (Step 5 Stage F shell entry placeholder)"
+
+[[bin]]
+name = "openpencil-app"
+path = "src/main.rs"
+
+[features]
+default = []
+shell-native = []

crates/openpencil-app/src/main.rs

@@ -0,0 +1,6 @@
+// OpenPencil application entry point.
+// Stage F cutover replaces this skeleton with the real shell host.
+
+fn main() {
+    println!("openpencil-app placeholder (Step 0 skeleton — see kickoff spec §2 Step 5)");
+}