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

README.md

@@ -120,6 +120,10 @@ func Main() -> int {
 | **Error Handling** | `Result<T,E>`, `Option<T>`, and the `?` operator |
 | **Standard Library** | `Io`, `Array`, `String`, `Map` |
 | **Backend** | C transpiler (bootstrap) |
+| **Gradual Ownership** | `@[Checked]` + `&T`/`&mut T` borrow checking |
+| **CTFE** | `const func` — compile-time function execution |
+| **Trait Bounds** | `func Max<T: Comparable>(a: T, b: T) -> T` |
+| **Package Manager** | `bux add`, `bux install`, `bux.lock`, path + git deps |
 | **Tooling** | `bux new`, `bux build`, `bux run`, `bux check` |
 
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