feat: V2 phase 3A — VDBE core (interpreter, registers, control/result/arithmetic/compare opcodes)

[iheitlager]

Refs: 009/Req-1, 009/Req-2, 009/Req-3, 009/Req-4
Part of epic #56, V2 phase 3 (0.7.0). Depends on: #78 (kernel) + #87 (frozen opcode set) + #88 (spec 009). Can start the moment #78 lands — does not wait for the parser (#61).

Scope (src/vdbe/)

• Instruction/Opcode/Program types per spec 009; register file of Values
• Fetch-decode-execute loop: Init/Goto/Halt/Return/Once, conditional jumps (IfNot/IfPos/IfNotZero/DecrJumpZero, IsNull/NotNull), OffsetLimit counters
• Result ops: Integer/String8/Null/Copy/MakeRecord/ResultRow
• Arithmetic (Add/Subtract/Multiply/Divide/Remainder) and comparisons (Lt/Le/Gt/Ge/Eq/Ne) — all value semantics delegated to src/semantics (spec 008); zero semantic logic in the opcode bodies
• Coercion ops: RealAffinity/MustBeInt/CollSeq via kernel apply_affinity/collation registry
• Acceptance oracle: spike 008's expression vectors (tests/corpus/expr_vectors/) reproduce bit-exact through hand-assembled programs — the ratchet pays off here, before any codegen exists

Assurance obligations

mvl-limit clean; no-panic totality (bad programs → structured Err, never panic; fuzz target on arbitrary instruction streams); per-scenario Tests links in spec 009; #65's dashboard line starts counting opcodes-implemented.

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🤖 Generated with Claude Code

[iheitlager]

Complexity

Large — new module surface (program.rs, exec.rs, control.rs, arithmetic.rs, result.rs) plus two kernel gaps (checked_div/checked_rem in coerce.rs, record encoder in src/record/) plus fuzz target and oracle-vector test harness.

Token budget: large tier.

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🤖 Analysis by Claude