feat(ownership): preserve function parameter capabilities through MIR

[dporkka]

Summary

Stacked on #384.

Preserves source-level function parameter capabilities through HIR into MIR's existing Local.cap metadata.

• HIR FunctionDef now carries a capability vector aligned with params
• explicit params and using params retain their declared capability
• compiler-generated typeclass dictionary params are marked ref
• MIR FunctionBuilder gains add_param_with_cap
• HIR → MIR lowering stores the capability on each parameter local
• lowering rejects misaligned parameter/capability metadata instead of silently truncating
• adds focused HIR and MIR regression tests
• updates direct HIR test fixtures

Why

Nulang's capability checker already models linear/unique ownership, but HIR previously erased parameter capabilities. The Drop planner therefore could not distinguish an ownership-transfer parameter from a borrowed/shared parameter.

This patch changes no calling convention and no runtime behavior. It only preserves metadata required for a later sound sink/ownership-flow optimization.

Stack

Depends on #384 (consume runtime move-out).

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