refactor: inherit Clippy lint config and Rust edition from workspace (#3782)

* refactor: inherit Clippy lint config and Rust edition from workspace

This also ensures developers running `clippy lint` locally get the same
lints as during CI, especially when the Rust toolchain version is fixed
through a `rust-toolchain.toml` file.

* chore(clippy.toml): bump MSRV to 1.87

apps/app-playground/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "theseus_playground"
 version = "0.0.0"
-edition = "2024"
+edition.workspace = true
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -9,3 +9,6 @@ edition = "2024"
 theseus = { workspace = true, features = ["cli"] }
 tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }
 enumset.workspace = true
+
+[lints]
+workspace = true