comptime VM: dedicated Type builtin TypeId (8B), distinct from .any — foundation (dead)

Add TypeId.type_value (slot 19) + matching TypeInfo.type_value variant: an
8-byte type handle, distinct from the 16-byte boxed .any. All types.zig layout
handlers wired (size/align 8, display "Type", hash/eql); toLLVMTypeInfo -> i64.

Reserve builtin headroom: first_user 19 -> 100 (slots 20-99 padded with the
unresolved tripwire) so future builtins don't renumber user TypeIds / churn
sx ir snapshots. 22 IR snapshots regenerated (pure renumber to 100-base).

type_resolver still returns .any for "Type" — nothing produces .type_value
yet, so no behavior change. 697/0 both gates.

current/CHECKPOINT-COMPILER-API.md

@@ -335,6 +335,23 @@ when reached (sentinels or accessor fns; see the design doc Risks).
   `List` growth; orthogonal, see `current/CHECKPOINT-METATYPE.md`.)
 
 ## Log
+- **Phase 3 P3.4 step 2 (VM plan) — dedicated `Type` builtin TypeId: FOUNDATION landed (dead/additive) (2026-06-18).**
+  Added `TypeId.type_value` (slot 19) + a matching `TypeInfo.type_value` variant + the builtins
+  init entry — an **8-byte type handle distinct from the 16-byte boxed `.any`** (THE WALL). All
+  `types.zig` layout handlers wired: `sizeOf`/`typeSizeBytes` → 8, `typeAlignBytes` → 8,
+  `typeName` → "Type", `hashTypeInfo`/`typeInfoEql` no-payload arms. Only ONE exhaustive switch
+  needed a new arm (`backend/llvm/types.zig` `toLLVMTypeInfo` → `cached_i64`); every other
+  `switch(TypeInfo)` site has an `else` (audited when the resolver flips). **`first_user` 19 → 100**
+  (per the user): slots 20–99 are RESERVED builtin headroom (infos padded with the `unresolved`
+  tripwire), so future builtins don't renumber user TypeIds / churn `sx ir` snapshots. Cost:
+  ~80 default entries in each binary's per-type reflection arrays (user opted in). **Still dead:**
+  `type_resolver.zig:64` STILL returns `.any` for "Type" — nothing produces `.type_value` yet, so
+  NO behavior change. Regenerated 22 IR snapshots (pure TypeId renumber to 100-base; `git diff
+  --name-only` confirmed ONLY `.ir` files + the 2 source files changed — no stdout/stderr/exit).
+  **697/0 both gates** (OFF and `-Dcomptime-flat`). **Next:** flip `type_resolver:64` →
+  `.type_value`, then migrate the `.any` refs that mean "a Type value" (const_type result /
+  reflection returns / metatype `Type` params / `.type_tag` checks) — leave the real boxed-Any
+  refs — file-by-file with a build after each.
 - **Phase 3 P3.4 step 1 (VM plan) — lowering-time default context; first blocker cleared (2026-06-18).**
   `materializeDefaultContext` now falls back to a ZEROED `Context` (found by name) when the
   `__sx_default_context` global is absent — i.e. at LOWERING time, where the global isn't