test(wand): record the trailing-fence ambiguity as a decision

A bare fence on the last line closes the wrapper in every well-formed
response and is content only when generation stopped exactly on an
embedded delimiter. Nothing separates the two, so assert the chosen
behavior instead of leaving it implicit.

Author: waleedlatif1

apps/sim/lib/wand/strip-code-fences.test.ts

@@ -45,6 +45,14 @@ describe('stripCodeFences', () => {
     expect(stripCodeFences(truncated)).toBe('const md = `\n```\nhello\n`;\nreturn md;')
   })
 
+  it('treats a trailing bare fence as the closer even when the body was truncated at one', () => {
+    // Irreducibly ambiguous: a trailing bare fence closes the wrapper in every
+    // well-formed response, and is content only when generation stopped exactly
+    // at an embedded delimiter. Declining to strip it would leave a stray fence
+    // in the common case, which is the bug this util exists to fix.
+    expect(stripCodeFences('```javascript\nconst md = `\n```')).toBe('const md = `')
+  })
+
   it('preserves a fenced docstring inside a Python body', () => {
     const fenced = '```python\ntemplate = """\n```sql\nSELECT 1\n```\n"""\nreturn template\n```'
     expect(stripCodeFences(fenced)).toBe(

apps/sim/lib/wand/strip-code-fences.ts

@@ -88,7 +88,10 @@ export function stripCodeFences(text: string): string {
   while (inner.length > 0 && inner[inner.length - 1].trim() === '') inner.pop()
 
   // Only the very last line may close the wrapper. A truncated response simply
-  // has no closer, and every line after the opener survives.
+  // has no closer, and every line after the opener survives. The one case this
+  // cannot get right is generation stopping exactly on an embedded delimiter,
+  // where that final line is content — indistinguishable from a real closer, and
+  // rarer than the wrap it would otherwise fail to strip.
   if (inner.length > 0 && FENCE_LINE.test(inner[inner.length - 1])) inner.pop()
 
   while (inner.length > 0 && inner[0].trim() === '') inner.shift()