Fix vocabulary induction loop running too late

The loop slept 24h before its first pass, so suggestions would never
appear unless the server was up for a full day. Move the sleep to the
end so the first induction pass runs ~30s after startup.

drb-c2-core/app/internal/vocabulary_learner.py

@@ -250,8 +250,8 @@ async def vocabulary_induction_loop() -> None:
         f"interval: {settings.vocabulary_induction_interval_hours}h, "
         f"sample budget: {settings.vocabulary_induction_sample_tokens} tokens"
     )
+    await asyncio.sleep(30)  # short startup grace period before first pass
     while True:
-        await asyncio.sleep(interval)
         try:
             flags = await get_flags()
             if flags["vocabulary_learning_enabled"]:
@@ -260,6 +260,7 @@ async def vocabulary_induction_loop() -> None:
                 logger.info("Vocabulary learning disabled — skipping induction pass")
         except Exception as e:
             logger.error(f"Vocabulary induction pass failed: {e}")
+        await asyncio.sleep(interval)
 
 
 async def _run_induction_pass() -> None: