feat: Python parity for Wave 6-8 — memory admin / cooking / leftoff / trivia / routines

New module `wave68_handlers.py` (~270 lines) covering the Rust packs that
were Rust-only after Waves 6-8:

  - memory_admin: do_memory_count/list/wipe (with full RU plural decl.)
  - cooking: do_cooking + reusable match_recipe(phrase) for the 15-dish
    preset table. Schedules a "ready!" reminder via scheduler_store.
  - leftoff: do_leftoff stitches memory + scheduled tasks + last reply
    into a one-paragraph recap. Offline.
  - trivia: do_trivia random one-liner from RU/EN MCU pools.
  - routines: do_good_night (sleep profile + cancel one-shots),
    do_good_morning (default profile + agenda hint),
    do_coffee_break (5-min check-in via scheduler).

memory_store: new clear_all() returning removed count, atomic via _save.

extensions.py: imports + set_speak wiring + 9 proxy do_* fns.
main.py: 9 new dispatch elifs.
commands.yaml: 9 new entries (now 196 total).

tests/test_wave68_handlers.py: 15 unit tests covering each handler.
Test helper `_rewire()` re-imports state modules via the existing
isolated_state fixture then re-binds the wave68_handlers module-level
refs — fixes the gotcha where module-level imports cache the OLD
memory_store / scheduler_store instances from process startup.

Tests: 81 → 96 (+15).

memory_store.py

@@ -96,6 +96,17 @@ def forget(key: str) -> bool:
     return False
 
 
+def clear_all() -> int:
+    """Wipe every fact. Returns count of removed entries. Atomic via _save."""
+    _load()
+    n = len(_store)
+    if n == 0:
+        return 0
+    _store.clear()
+    _save()
+    return n
+
+
 def search(query: str, limit: int = 5) -> list[dict]:
     _load()
     nq = _normalize_key(query)