refactor(tools): move model-interaction tools to the agent_tools registry (#4445)

Moves chat_with_model, ask_teacher and list_models out of ai_interaction.py
into src/agent_tools/model_interaction_tools.py (the do_ prefix dropped) and
registers them in TOOL_HANDLERS, so dispatch flows through the registry instead
of the dispatch_ai_tool elif in tool_execution.py.

The implementations are relocated, not wrapped. ai_interaction.py keeps only
the shared helpers they reuse (_resolve_model, AI_CHAT_TIMEOUT), still used by
the not-yet-migrated session/pipeline tools. dispatch_ai_tool loses its three
now-unused branches.

Also removes the dead do_second_opinion: it was already off the live tool
surface (no tag/schema/parsing/dispatch; tool_index.py notes it was removed),
so the function and its stale frontend catalog entries (admin.js, assistant.js)
are deleted.

Tests: owner-scope test points at the new list_models location and drops the
moved tools from the dispatch_ai_tool parametrize; a new
test_model_interaction_registry covers registration, owner threading, and
registry dispatch.

src/tool_execution.py

@@ -766,10 +766,19 @@ async def _execute_tool_block_impl(
         query = content.split("\n")[0].strip()
         desc = f"search_chats: {query[:80]}"
         result = await do_search_chats(query, owner=owner)
-    elif tool in ("chat_with_model", "create_session", "list_sessions",
+    elif tool in ("chat_with_model", "ask_teacher", "list_models"):
+        # Migrated to the agent_tools registry (#3629): dispatched through
+        # TOOL_HANDLERS with the owner/session ctx these tools need, instead
+        # of the legacy dispatch_ai_tool elif. The do_* impls stay in
+        # ai_interaction.py (dispatch_ai_tool + the owner-scope test use them).
+        first_line = content.split(chr(10))[0].strip()[:60]
+        desc = f"{tool}: {first_line}" if first_line else tool
+        result = await _document_tool_dispatch(tool, content, session_id, owner) \
+            or {"error": f"{tool}: execution failed", "exit_code": 1}
+    elif tool in ("create_session", "list_sessions",
                   "send_to_session", "pipeline",
-                  "manage_session", "manage_memory", "list_models",
-                  "ui_control", "ask_teacher"):
+                  "manage_session", "manage_memory",
+                  "ui_control"):
         from src.ai_interaction import dispatch_ai_tool
         desc, result = await dispatch_ai_tool(tool, content, session_id, owner=owner)
     elif tool == "manage_tasks":