Stage S-1b: dictionary word ids grow with the dictionary; a word that can't get an id is refused whole (FABRIC-3.9.0 §8.1)

- word_id_map / recycled_word_ids are heap tables (one shared capacity,
  64 doubling), grown all-or-nothing by allocate-copy-free. Numbering is
  unchanged, so boot parity is unchanged.
- vm_create_word() takes the id before linking; on failure it frees the
  entry, sets vm->error, logs LOG_ERROR and counts
  (vm_dictionary_word_id_refusals()). No word runs with WORD_ID_INVALID.
- Readers of the id space bound by vm->next_word_id, not DICTIONARY_SIZE.
- transition_heat gets its own capacity and grows on record (was sized
  once -- a heap overflow under a dynamic bound); every reader bounds by it.
- Stadium id->cell rows start empty and grow on dispatch; a failed grow is
  logged, counted and not admitted. S-2 (the cell pool) stays open.

Probe (reverted), identical on amd64/aarch64/riscv64: +2000 words get real
ids (capacity 4096); a word at id 2738 lands 200x in the rolling window and
is Stadium-admitted; FORGET recycles across the old boundary; an injected
grow failure refuses the word whole (NULL, error, counter, dictionary
unchanged) and the retry succeeds. 3-ISA acceptance passes; boot parity
(531, 0x572daac83b797332) and the dict_hash set unchanged.

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

include/starkernel/vm/stadium_words.h

@@ -48,7 +48,8 @@
 
 /*
  * stadium_words_init - Allocates and zeroes the word_id -> cell_index map
- * (DICTIONARY_SIZE entries per VM quota slot, stadium_max_vm_count() slots,
+ * (one row per VM quota slot, stadium_max_vm_count() slots; since S-1b each
+ * row starts empty and grows on dispatch, no longer DICTIONARY_SIZE entries;
  * kmalloc'd -- was a flat static array before 2026-08-15, when the VM count
  * bound became RAM-derived rather than a compile-time constant). Must be
  * called after stadium_boot_init() and stadium_birth_hera(), before any word
@@ -97,8 +98,10 @@ void stadium_words_init(void);
  * the failed attempt). On success, records the mapping and increments the
  * promotion counter.
  *
- * No-op if word_id == WORD_ID_INVALID, word_id >= DICTIONARY_SIZE, or vm_id
- * holds no Stadium quota.
+ * No-op if word_id == WORD_ID_INVALID or vm_id holds no Stadium quota. A
+ * word_id past the slot's row grows the row first (S-1b); if that fails the
+ * dispatch is not admitted, logged and counted
+ * (stadium_words_row_grow_failures()).
  *
  * @param vm_id           Owning VM -- vm->stadium_vm_id at every call site.
  *                        Scopes the word_id -> cell_index lookup to this
@@ -140,7 +143,7 @@ void stadium_word_forget(VMUuid vm_id, uint32_t word_id);
  * Bob's ruling 2026-08-06) can add this as an explicit term instead of
  * silently omitting word-execution heat it has no other way to see.
  *
- * Walks all DICTIONARY_SIZE word_slots for vm_id's quota slot; each
+ * Walks all of the word_slots row for vm_id's quota slot; each
  * resident entry contributes its cell's current heat, verified live against
  * the discriminator bitmap (same self-healing pattern as
  * resolve_resident_cell() -- a stale map entry contributes 0, not garbage).
@@ -161,6 +164,9 @@ uint64_t stadium_words_resident_heat(VMUuid vm_id);
  */
 void stadium_words_stats(VMUuid vm_id, uint64_t *promotions, uint64_t *evictions);
 
+/* S-1b: dispatches not admitted because a slot's word row couldn't grow. */
+uint64_t stadium_words_row_grow_failures(void);
+
 /*
  * stadium_words_print_boot_diagnostics - Console output satisfying item
  * 4.1's "observable via a diagnostic word or boot console output"