docs(spec): clarify has index guard

packages/spec/src/automation/flow-value-slot-template.test.ts

@@ -198,7 +198,7 @@ describe('a head CEL claims is read through `vars`, the route a `$`-named head t
     expect(refusalOf('{record.true}')).not.toContain('the guarded form');
   });
 
-  it('an index anywhere in the path leaves it unguarded — `has()` refuses one at run time', () => {
+  it('an indexed intermediate segment stays unguarded even though `has()` accepts it at run time', () => {
     expect(refusalOf('{rows.0.name}')).toContain("source: 'rows[0].name' }");
     expect(refusalOf('{rows.0.name}')).not.toContain('the guarded form');
   });

packages/spec/src/automation/flow-value-slot-template.ts

@@ -315,10 +315,10 @@ type Write = (source: string) => string;
 
 /**
  * A `has()` guard for a path of keys — the absent-variable and absent-key
- * remedy. `has()` takes a field selection over names alone: an index anywhere
- * in its argument (`has(a[0].b)`, `has(vars["$x"].y)`) is refused when it
- * runs, so a path with a numeric segment, a `$`-named head or a keyword
- * segment gets no guard.
+ * remedy. `has()` refuses an index only when it is the final selection in its
+ * argument. A path with a numeric segment still gets no guard because this
+ * guard builder only emits field selections over names; `$`-named heads and
+ * keyword segments likewise get no guard.
  *
  * The guard tests one step at a time, from `vars`, which holds only the
  * variables the run has bound: `has(vars.source) && has(vars.source.id) ?