fix: keep embedded session controls visible and handle empty memory

Cap the embedded shell at its portal container height so steering and stop controls remain accessible. Skip vector retrieval for an empty authoritative Memory archive and compute SQL-rule embeddings lazily.

Validated with 54 Memory tests, 90 frontend tests, five browser scenarios, frontend and Docker builds, and a read-only comparison against the real empty Memory archive.

harness/tht/cli/memory_cmd.py

@@ -296,6 +296,7 @@ def rules_cmd(question: str, session: str = typer.Option(..., "--session"),
               filters: str = typer.Option("{}", "--filters"),
               json_out: bool = typer.Option(False, "--json"), config: Path = CONFIG_OPT):
     """Consult SQL rules and explained errors in schema linking and SQL construction."""
+    from functools import cache
     from types import SimpleNamespace
 
     from tht.cli.vector_cmd import make_embedder, open_searcher
@@ -307,8 +308,8 @@ def rules_cmd(question: str, session: str = typer.Option(..., "--session"),
         if current_phase(snapshot) not in {4, 6, 7}:
             raise ValueError("Memory rules are consulted in schema linking or SQL construction")
         scope = _recall_scope(cfg, filters)
-        vector = make_embedder(cfg.embeddings).embed_query(question)
-        embedder = SimpleNamespace(embed_query=lambda _: vector)
+        # Share one vector across both families, but only when the archive has cards.
+        embedder = SimpleNamespace(embed_query=cache(make_embedder(cfg.embeddings).embed_query))
         searcher = open_searcher(cfg)
         candidates = []
         for family in ("sql_rule", "explained_error"):