comptime VM: Phase 3 — find_type + type_field_count reflection readers

First read-only compiler-API reflection readers, bound the same way as the
intern/text_of seed (compiler_lib.bound_fns + Vm.callCompilerFn, native on flat
memory, no marshaling). A type handle is a plain u32 TypeId (like StringId), so
both stay clean scalar host-calls:

  find_type(name: StringId) -> TypeId          (TypeTable.findByName; unresolved/0 if absent)
  type_field_count(t: TypeId) -> i64           (new TypeTable.memberCount; loud-bail, no silent 0)

memberCount is the single source both the legacy handler and the VM read, so the
two paths can't drift. find_type returns a non-optional TypeId using the
unresolved(0) sentinel for not-found rather than ?Type — a Type value is
.any-typed (which the flat-memory VM does not represent) and an optional can't
cross the legacy<->VM eval boundary; unresolved is the project-blessed "no type"
marker.

Example 0628 chains intern -> find_type -> type_field_count (+ a not-found
lookup), folded at #run, VM-HANDLED natively. VM unit test added.

Parity 689/689 (gate OFF and -Dcomptime-flat).

examples/0628-comptime-compiler-find-type.sx

@@ -0,0 +1,37 @@
+// Comptime compiler API — read-only reflection readers (Phase 3).
+//
+// `find_type` / `type_field_count` are bound to the `compiler` library via
+// `abi(.zig) extern compiler`, joining the `intern` / `text_of` seed. They are
+// the first REFLECTION readers: the compiler exposes its own type table to
+// comptime sx as plain handles (a `TypeId` is a u32, like a `StringId`), so the
+// calls are clean scalar host-calls — handle in, scalar out, no marshaling.
+//
+//   find_type(name)        → the named type's handle (0 / `unresolved` if absent)
+//   type_field_count(t)    → its member count (struct fields here)
+//
+// Comptime-only: they run inside `#run`, folding to plain int constants the
+// runtime `main` prints. Chains `intern` → `find_type` → `type_field_count`.
+
+#import "modules/std.sx";
+
+compiler :: #library "compiler";
+
+StringId :: u32;
+TypeId   :: u32;
+
+intern           :: (s: string) -> StringId abi(.zig) extern compiler;
+find_type        :: (name: StringId) -> TypeId abi(.zig) extern compiler;
+type_field_count :: (t: TypeId) -> i64 abi(.zig) extern compiler;
+
+Point :: struct { x: i64; y: i64; z: i64; }
+
+// Look the struct up by name and count its fields, all at comptime.
+point_fields :: #run type_field_count(find_type(intern("Point")));
+
+// A name with no matching type folds to the `unresolved` sentinel (0).
+missing_id :: #run find_type(intern("NoSuchType"));
+
+main :: () {
+    print("Point has {} fields\n", point_fields);
+    print("missing type id = {}\n", missing_id);
+}

examples/expected/0628-comptime-compiler-find-type.exit

@@ -0,0 +1 @@
+0

examples/expected/0628-comptime-compiler-find-type.stderr

@@ -0,0 +1 @@
+

examples/expected/0628-comptime-compiler-find-type.stdout

@@ -0,0 +1,2 @@
+Point has 3 fields
+missing type id = 0