fix: restore spec_version indentation in config.py (inside class)

The version bump edit accidentally removed indentation, making
spec_version a module-level variable instead of a Pydantic class field.

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: tbitcs

src/specsmith/config.py

@@ -85,7 +85,7 @@ class ProjectConfig(BaseModel):
         description="Target platforms",
     )
     language: str = Field(default="python", description="Primary language/runtime")
-spec_version: str = Field(default="0.3.0", description="Spec version to scaffold from")
+    spec_version: str = Field(default="0.3.0", description="Spec version to scaffold from")
     description: str = Field(default="", description="Short project description")
 
     # Options