Add deprecated feature and migrate string_proc to just_fmt

- Add `deprecated` feature flag to Cargo.toml
- Gate `string_proc` module behind both `deprecated` and `string_proc`
  features
- Replace internal `string_proc` dependency with `just_fmt` crate in
  constants macros
- Mark all `string_proc` modules as deprecated with migration
  instructions
- Remove `string_proc` dependency from sheet system

1 files changed, 0 insertions, 1 deletions

diff --git a/systems/sheet/Cargo.toml b/systems/sheet/Cargo.toml
index 5c53c36..99cc7c7 100644
--- a/systems/sheet/Cargo.toml
+++ b/systems/sheet/Cargo.toml
@@ -5,5 +5,4 @@ version.workspace = true
 
 [dependencies]
 sheet_system_macros = { path = "macros" }
-string_proc = { path = "../../utils/string_proc" }
 asset_system = { path = "../_asset" }