fix: body-local #run of an unbridged shape fails loudly instead of silent garbage (issue 0182)

The body-local #run fold in emitCall was effectively dead (gated on
args.len==0, but the __ct comptime wrapper always carries the implicit
*Context arg), so every body-local #run fell through to a RUNTIME call:
bridgeable shapes lucked into the right value; an unbridgeable shape
(e.g. [2][]i64) ran over --- storage -> garbage, exit 0, no diagnostic.

Fold any is_comptime callee (gated !enclosing.is_comptime so nested
metatype calls in a comptime wrapper's dead body aren't folded). On a
tryEval bail, distinguish a BRIDGE bail (result can't regToValue-
materialize -> error: comptime init of 'X' failed: <reason> +
comptime_failed, build fails, symmetric with the global #run path) from
an EXECUTION bail (VM can't run the body, e.g. NaN/extern -> runtime
fallthrough, preserving types/0150), via comptime_vm.last_bail_was_bridge
(reset at tryEval entry, set only at regToValue). The const name is
threaded onto the wrapper (comptime_display_name) so the diagnostic reads
the source name, not __ct_N.

Regressions: diagnostics/1204 (negative), comptime/0645 (positive).
Verified by 3 adversarial reviews, suite 801/0.

examples/comptime/0645-comptime-body-local-run-bridgeable.sx

@@ -0,0 +1,28 @@
+// A body-local `#run` const of a BRIDGEABLE shape — a scalar, a struct, an
+// array, or an `?Array` optional — evaluates and produces its const value.
+// These are the common cases that must keep working alongside the issue-0182
+// fix (which fails ONLY the unbridgeable-result case, e.g. `[2][]i64`).
+//
+// Regression (issue 0182): the body-local `#run` fold must not regress the
+// bridgeable cases when it learned to fail loudly on an unbridgeable result.
+#import "modules/std.sx";
+
+Pt :: struct { x: i64; y: i64; }
+
+mk_scalar :: () -> i64 { return 42; }
+mk_struct :: () -> Pt { return .{ x = 3, y = 4 }; }
+mk_arr :: () -> [3]i64 { r : [3]i64 = ---; r[0] = 10; r[1] = 20; r[2] = 30; return r; }
+mk_opt :: () -> ?[3]i64 { r : [3]i64 = ---; r[0] = 1; r[1] = 2; r[2] = 3; return r; }
+
+main :: () {
+    N :: #run mk_scalar();
+    S :: #run mk_struct();
+    A :: #run mk_arr();
+    O :: #run mk_opt();
+
+    print("N={}\n", N);
+    print("S={} {}\n", S.x, S.y);
+    print("A={} {} {}\n", A[0], A[1], A[2]);
+    v := O!;
+    print("O={}\n", v[1]);
+}

examples/comptime/expected/0645-comptime-body-local-run-bridgeable.exit

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

examples/comptime/expected/0645-comptime-body-local-run-bridgeable.stderr

@@ -0,0 +1 @@
+

examples/comptime/expected/0645-comptime-body-local-run-bridgeable.stdout

@@ -0,0 +1,4 @@
+N=42
+S=3 4
+A=10 20 30
+O=2