issues: promote 6 fixed bug repros to focused regression tests

All six produce their target outputs cleanly today; renamed out of
the `issue-*` namespace per CLAUDE.md "Resolving an open issue":

| Old                  | New                                       |
|----------------------|-------------------------------------------|
| issue-0032           | 181-impl-duplicate-same-file              |
| issue-0041           | 182-compound-type-in-expression           |
| issue-0042           | 183-type-alias-size-align                 |
| issue-0044           | 184-objc-defined-class-method-self        |
| issue-0045           | 185-pack-fn-comptime-return               |
| issue-0046           | 186-nested-comptime-return                |

Comment headers tightened to feature-focused (drop the issue-NNNN
provenance — that's in git history now). Missing expected `.txt` /
`.exit` files captured for 0041 + 0042 (they were untracked because
the bugs were fixed silently in adjacent work).

`examples/issue-*` after this commit: just `issue-0030.sx` — a
feature request (`extern G : T;` cross-file globals) that's never
been implemented. Staying in the issue namespace as a parked
proposal until the feature lands or gets formally rejected.

220/220 example tests + `zig build test` green.

examples/186-nested-comptime-return.sx

@@ -0,0 +1,31 @@
+// Nested comptime call + return — a comptime fn (`$x: s32`) whose
+// body contains BOTH a nested comptime call (`print`) AND a
+// `return X;` statement must lower cleanly. The wrapper fn built
+// by `createComptimeFunction` saves/restores `inline_return_target`
+// so it doesn't inherit a slot belonging to the OUTER caller's
+// basic block. Pre-fix: interp executed the wrapper with a
+// stale-frame inline-return slot and tripped a null-pointer store
+// at `storeAtRawPtr`.
+//
+// Repro: comptime fn (`$x: s32`) whose body has BOTH a nested
+// comptime call (`print`) AND a `return X;` statement. Pre-fix:
+// interp panics. Post-fix: prints "inside" then "n=42".
+//
+// The pack-fn variant of the same bug (filed in the original
+// issue as face 2) was fixed earlier when step-2b moved pack-fn
+// calls off the inline path into the mono path. Plain comptime
+// fns stay on the inline path; their fix is the
+// `createComptimeFunction` state save/restore.
+
+#import "modules/std.sx";
+
+helper :: ($x: s32) -> s64 {
+    print("inside\n");
+    return 42;
+}
+
+main :: () -> s32 {
+    n := helper(7);
+    print("n={}\n", n);
+    return 0;
+}