P5.7 Step C: delete interp.zig — the comptime VM is the sole evaluator

The legacy tagged-Value Interpreter is gone. Relocate the Value result-DTO
+ decodeVariantElements into a new comptime_value.zig (the VM<->host
materialization boundary); repoint comptime_vm/emit_llvm/ir-barrel Value to
it and BuildConfig to compiler_hooks; delete the dead valueToReg bridge;
slim compiler_lib.zig to just the name registry (BoundFn{sx_name} + bound_fns
+ findFn — weldedCompilerFn only validates names); simplify printInterpBailDiag
to comptime_vm.last_bail_reason; drop the unused interp_mod import in lower.zig.
rm src/ir/interp.zig + interp.test.zig.

Value is relocated (not eliminated): it survives only as the slim result DTO
at the VM->valueToLLVMConst boundary; the execution-time marshaling the VM
pivot targeted is gone. Drop dead Value.asString/reflectTypeId.

706/0 corpus + 476/476 unit.

current/CHECKPOINT-COMPILER-API.md

@@ -431,6 +431,30 @@ when reached (sentinels or accessor fns; see the design doc Risks).
   `List` growth; orthogonal, see `current/CHECKPOINT-METATYPE.md`.)
 
 ## Log
+- **P5.7 Step C — DELETED `interp.zig` (the legacy tagged-`Value` interpreter); the VM is the SOLE comptime
+  evaluator (2026-06-19).** Five green commits. **C1** (`#insert` → VM): `evalComptimeString` was the last
+  caller of `Interpreter.call`; routed through `comptime_vm.tryEval` (the VM bails-not-panics on malformed
+  lowering-time IR like 0737's `ret Ref.none`; `regToValue` dupes the result string into the lowering allocator).
+  **C2a** (ops.zig inline comptime-call fold → VM): the `emitCall` zero-arg comptime-callee fold now uses
+  `tryEval`. **C2b** (emit_llvm): dropped the `*const Interpreter` materialization param from `valueToLLVMConst`/
+  `serializeAggregateValue` (it was used ONLY for the `.heap_ptr` data arm, which the VM's `regToValue` never
+  produces) + the dead `interp_inst`. **C3** (the atomic delete, done by a delegated worker + independently
+  verified): moved the `Value` result-DTO + `decodeVariantElements` into a new `src/ir/comptime_value.zig`
+  (the VM↔host materialization boundary type); repointed `comptime_vm`/`emit_llvm`/`ir.zig`-barrel `Value` to it
+  and `BuildConfig` to `compiler_hooks`; deleted the dead `valueToReg` bridge; slimmed `compiler_lib.zig` to just
+  the name registry (`BoundFn{sx_name}` + `bound_fns` + `findFn`, all names preserved — `weldedCompilerFn` only
+  validates names; deleted `FnHandler` + all `handle*` + the `Interpreter`/`Value`/`InterpError` imports);
+  simplified `main.printInterpBailDiag` to use only `comptime_vm.last_bail_reason`; dropped the unused
+  `interp_mod` import in `lower.zig`; **`rm src/ir/interp.zig` (2383 lines) + `src/ir/interp.test.zig` (844
+  lines)** + their barrel entries. **DEVIATION from the plan's literal "delete Value":** `Value` is RELOCATED
+  (not eliminated) as the slim result/materialization DTO — the byte-addressable VM executes natively, and
+  `Value` survives ONLY at the VM→`valueToLLVMConst` boundary (the marshaling the pivot killed was at EXECUTION
+  time, which is gone). Eliminating it entirely (materializing LLVM consts straight from VM `Machine` bytes) is a
+  larger, riskier rewrite deferred as optional follow-up; the plan's PRIMARY goal — ONE evaluator, no legacy
+  interpreter, no fallback — is fully met. **706/0 corpus + 476/476 unit** (−24 from the deleted interp unit
+  tests + 1 `valueToReg` round-trip test). Also dropped dead `Value.asString`/`reflectTypeId` (no callers).
+  NEXT: Step D — re-express `define`/`make_enum` as sx over the compiler-API (they were legacy interp arms);
+  Step E — land the 0141 repro + finalize.
 - **P5.7 Step B — deleted the `#compiler`/`compiler_call`/hook-Registry mechanism end-to-end (2026-06-19).**
   All superseded by `abi(.compiler)` VM-native dispatch (P5.5) — no sx code emits any of it. Two green commits:
   **B1** (`e2971f2`) removed the `compiler_call` IR op: the op variant + `CompilerCall` struct (`inst.zig`), the