Implement array and slice value semantics

[itsfuad]

Goal

Finish owned dynamic-array operations and non-owning slice views while keeping mutation on projection/place lowering.

Current Model

• [N]T is fixed inline array storage.
• []T is owned dynamic-array storage and is move-only.
• &[]T is a shared slice view.
• &mut []T is a mutable non-resizing slice view.
• Slice views are reference forms; there is no standalone [T] slice type.
• Slice sources may be fixed arrays or dynamic arrays; slicing creates a view, not ownership.
• @expr produces rawptr; &expr and &mut expr create safe references.
• Ranges use .. for exclusive and ..= for inclusive bounds.

Progress

• PR Add semantic const evaluation #41 added semantic const evaluation and fixed-array const-index diagnostics.
• PR Implement array slice value semantics #42 established index assignment and range syntax.
• PR Implement dynamic array and reference semantics #44 added bounds-checked dynamic-array indexing, safe references, reference receivers, reborrows, borrowed interface dispatch, and mutable parameters.
• PR Lower dynamic array borrows as slice views #45 added canonical HIR/MIR SliceView construction and nested-place preservation.
• PR Implement scalar copy and runtime ownership semantics #48 migrates pointer syntax, lowers fixed-array and dynamic-array range slicing into fat views, enables slice-view indexing and mutable-view writes with bounds checks, and adds runtime plus negative fixtures.
• Dynamic-array reads and stores reuse MIR ProjectIndex, Load, and Store from Refactor MIR field/index access to projection places #32.

Remaining Work

• Add dynamic-array construction, allocation, and resize operations.
• Track indexed-place invalidation before allowing move-only element extraction.
• Preserve projection/place architecture from Refactor MIR field/index access to projection places #32; do not add one-off index or slice address nodes.
• Keep reference-origin and borrow-conflict work in Track reference origins and borrow conflicts #43.

Validation

• Parser, typechecker, HIR, MIR, and LLVM tests for construction, slicing, indexing, mutation, and bounds behavior.
• Positive and negative x_test fixtures.
• Runnable dynamic-array and slice-view smoke programs.
• Full capped Go test suite, vet, bundled compiler build, and diff checks.

[itsfuad]

PR #44 merged into main at merge commit 80b8ae9.

Completed in this batch: bounds-checked dynamic-array indexing, safe reference types/expressions, reference receivers and reborrows, borrowed interface dispatch, mutable parameters, and source fixtures. Remaining work stays open in the issue body: construction/resize, slice-view creation/indexing, receiver-view lowering, and indexed-place invalidation.