KOS_OP_UNPACK_FAST

• Style: EXTRA (FASTVAR, FASTVAR, NOARG, NOARG). Row: a0, a1 = fast local slot indices.

• Stack: [..., raw] → [...]. Pop TOS, PySequence_List, require len == 2, then KosNamespace_FastStore for slot a0 with seq[0] and slot a1 with seq[1] (same ownership rules as FAST_STORE: namespace increments ref as needed).

• Invariants: Frame namespace supports fast locals; both indices in range (same as FAST_STORE).

• Errors: ValueError if length ≠ 2; RuntimeError / NameError if fast namespace invalid or index out of bounds.

• Compiler form: Pre-compile extra tuple (slot0, slot1, 0, 0) with integer slot indices.

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5. Constants