feat: Phase 8.2, 8.4, 8.5, 9.1 + C backend fixes

Phase 8.2 — Gradual Ownership:
- Add tkRef/tkMutRef types and `mut` keyword
- Add @[Checked] attribute for opt-in borrow checking
- Reject assignment through &T in checked functions
- examples/ownership.bux

Phase 8.4 — CTFE:
- Evaluate const func at compile-time via evalExpr/evalBlock
- Fold const declarations to literals; emit #define in C
- examples/ctfe.bux (Factorial(10) → 3628800)

Phase 8.5 — Trait Bounds:
- Change declFuncTypeParams from seq[string] to seq[TypeParam] (name + bound)
- Parser handles <T: Comparable>
- Sema checks typeImplements at call sites
- Fix C backend: generic receivers + pointer self field access
- examples/trait_bounds.bux

Phase 9.1 — Package Manager:
- Inline tables/arrays in TOML parser
- bux add, bux install, bux.lock generation
- Dependency resolution with git/path sources
- Build pipeline merges dependency .bux sources

C Backend Fixes:
- resolveExprType(ekIdent) now applies typeSubst for generic params
- Method desugaring works for monomorphized generic receivers
- Pointer checks use isPointer (covers tkRef/tkMutRef)
- Field access on &T emits -> instead of .

Remove accidentally committed test binaries from tracking

src/ast.nim

@@ -272,6 +272,13 @@ type
     of skDecl:
       stmtDecl*: Decl
 
+  # ---------------------------------------------------------------------------
+  # Type Parameters (for generics with trait bounds)
+  # ---------------------------------------------------------------------------
+  TypeParam* = object
+    name*: string
+    bounds*: seq[string]   ## e.g. ["Comparable"] for <T: Comparable>
+
   # ---------------------------------------------------------------------------
   # Declarations
   # ---------------------------------------------------------------------------
@@ -325,13 +332,13 @@ type
       declFuncCallConv*: CallingConvention
       declFuncConst*: bool          ## const func — evaluable at compile time
       declFuncName*: string
-      declFuncTypeParams*: seq[string]
+      declFuncTypeParams*: seq[TypeParam]
       declFuncParams*: seq[Param]
       declFuncReturnType*: TypeExpr  ## nil if void/inferred
       declFuncBody*: Block           ## nil for signature-only
     of dkStruct:
       declStructName*: string
-      declStructTypeParams*: seq[string]
+      declStructTypeParams*: seq[TypeParam]
       declStructFields*: seq[StructField]
     of dkEnum:
       declEnumName*: string
@@ -345,7 +352,7 @@ type
       declInterfaceMethods*: seq[Decl]  ## FuncDecl signatures only
     of dkImpl:
       declImplTypeName*: string
-      declImplTypeParams*: seq[string]  ## type parameters for generic impl: extend Box<T>
+      declImplTypeParams*: seq[TypeParam]  ## type parameters for generic impl: extend Box<T>
       declImplInterface*: string        ## empty if not for interface
       declImplMethods*: seq[Decl]
     of dkModule: