FABRIC-3.10.8 K-8: free the vocabulary indexes and inference outputs at vm_cleanup

The ~3.4 KB/VM heap residual left after K-4 was each dead VM's CONTEXT
and FORTH first-character bucket arrays (84 blocks, 3,400 bytes per
worker), plus last_inference_outputs. New vocabulary_free_indexes();
both vm_cleanup()s call it and free the outputs. Per-VM residual is now
232 bytes: the registry node (kept by design) and the vm_physics node
(open finding). 3-ISA acceptance clean, hash 0x99b01134c3d3049c.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/word_source/include/vocabulary_words.h

@@ -98,4 +98,13 @@ void vocabulary_word_definitions(VM *vm);
  */
 void vocabulary_word_forth(VM *vm);
 
+/*
+ * @brief Free this VM's vocabulary search indexes (vm_cleanup())
+ * @details FABRIC-3.10.8 K-8: the CONTEXT and FORTH first-character bucket
+ *          arrays (vm->vocab.ctx_fc / forth_fc) were never freed -- about
+ *          3.4 KB left behind by every VM that died.
+ * @param vm Pointer to the virtual machine instance
+ */
+void vocabulary_free_indexes(VM *vm);
+
 #endif /* VOCABULARY_WORDS_H */