Use the stable toolchain

There is no need for nightly anymore*, and using stable will
save at aleast 1GB of space to store the nightly toolchain, and
safe about 20s that it takes to download and install it.

Of course, this also makes working on the project easier.
Let's be sure we set our minimal required version though.

*The need for it on Windows was fixed with the `file-id` crate
and a patch to it which hopefully soon will be merged.

Author: Byron

Cargo.lock

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [lib]
 doctest = false
 test = false

crates/but-action/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [lib]
 proc-macro = true
 

crates/but-api-macros/Cargo.toml

@@ -8,7 +8,7 @@ description = "A GitButler CLI tool"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 readme = "../../README.md"
 publish = false
-
+rust-version = "1.89"
 [features]
 
 [dependencies]

crates/but-api/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [lib]
 doctest = false
 test = false

crates/but-bot/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [dependencies]
 tokio = { workspace = true, features = ["full"] }
 serde.workspace = true

crates/but-broadcaster/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [dependencies]
 anyhow = "1.0.100"
 serde.workspace = true

crates/but-claude/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [lib]
 doctest = false
 

crates/but-core/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [dependencies]
 anyhow.workspace = true
 serde.workspace = true

crates/but-cursor/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2024"
 authors = ["GitButler <gitbutler@gitbutler.com>"]
 publish = false
-
+rust-version = "1.89"
 [lib]
 doctest = false
 test = false