Fix optimizer bug: TailCall inside If not converted on inline

When the tail-call pass converted a Call to TailCall inside an If branch,
and the inliner subsequently inlined that word, the TailCall was not
converted back to Call in nested control-flow bodies. The TailCall codegen
emits a Return instruction, which would exit the *caller* instead of just
the inlined callee — silently corrupting the return stack.

Root cause: the inliner only converted top-level TailCalls in the body
(line-by-line iteration), missing TailCalls nested inside If/DoLoop/Begin
structures.

Fix: add detailcall() that recursively walks the entire IR tree and
converts all TailCall ops back to Call before inlining.

This unblocks defining complex Forth words (like SM/REM, FM/MOD) that
use DABS → DNEGATE → D+ chains with return-stack operations inside
conditional branches.

426 tests pass (including new regression test).

crates/core/src/outer.rs

@@ -7944,6 +7944,18 @@ mod tests {
         assert_eq!(eval_stack("-1 0 10 WITHIN"), vec![0]);
     }
 
+    #[test]
+    fn test_inline_tailcall_rstack_interaction() {
+        // Regression: inlining a word that had a TailCall inside an If branch
+        // caused the TailCall's Return to exit the *caller*, corrupting the
+        // return stack. The fix: detailcall() recursively converts TailCall
+        // back to Call inside all nested control-flow bodies when inlining.
+        assert_eq!(
+            eval_stack(": T 42 >R 99 >R -7 -1 DABS R> R> ; T"),
+            vec![42, 99, 0, 7]
+        );
+    }
+
     #[test]
     fn test_do_loop_with_i_and_step() {
         // +LOOP with step of 2