feat(lexer): add type system keywords

Added four keywords for new type system:
- concept: Base type definition
- sub_concept: Enum/record sub-type definition
- concept_comparison: Compile-time enum mapping
- any: Universal type for dynamic contexts

Also added:
- CLAUDE.md with project instructions and commit guidelines
- Test coverage for new keywords
- Crate-level deny directives for unused variables and dead code

Fixed pre-existing clippy issues to pass pre-commit hooks.

src/syntax/ast.rs

@@ -105,14 +105,16 @@ pub enum Priority {
     Critical,
 }
 
-impl Priority {
-    pub fn from_str(s: &str) -> Option<Self> {
+impl std::str::FromStr for Priority {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
         match s {
-            | "low" => Some(Priority::Low),
-            | "normal" => Some(Priority::Normal),
-            | "high" => Some(Priority::High),
-            | "critical" => Some(Priority::Critical),
-            | _ => None,
+            | "low" => Ok(Priority::Low),
+            | "normal" => Ok(Priority::Normal),
+            | "high" => Ok(Priority::High),
+            | "critical" => Ok(Priority::Critical),
+            | _ => Err(()),
         }
     }
 }
@@ -126,7 +128,7 @@ pub struct Character {
     pub template: Option<Vec<String>>, // `from Template1, Template2`
     pub uses_behaviors: Option<Vec<BehaviorLink>>, // `uses behaviors: [...]`
     pub uses_schedule: Option<Vec<String>>, /* `uses schedule: ScheduleName` or `uses schedules:
-                                             * [...]` */
+                                        * [...]` */
     pub span: Span,
 }