feat: use endpoint metadata for custom model context and pricing (#1906)

* perf: cache base_url.lower() via property, consolidate triple load_config(), hoist set constant

run_agent.py:
- Add base_url property that auto-caches _base_url_lower on every
  assignment, eliminating 12+ redundant .lower() calls per API cycle
  across __init__, _build_api_kwargs, _supports_reasoning_extra_body,
  and the main conversation loop
- Consolidate three separate load_config() disk reads in __init__
  (memory, skills, compression) into a single call, reusing the
  result dict for all three config sections

model_tools.py:
- Hoist _READ_SEARCH_TOOLS set to module level (was rebuilt inside
  handle_function_call on every tool invocation)

* Use endpoint metadata for custom model context and pricing

---------

Co-authored-by: kshitij <82637225+kshitijk4poor@users.noreply.github.com>

model_tools.py

@@ -276,6 +276,7 @@ def get_tool_definitions(
 # The registry still holds their schemas; dispatch just returns a stub error
 # so if something slips through, the LLM sees a sensible message.
 _AGENT_LOOP_TOOLS = {"todo", "memory", "session_search", "delegate_task"}
+_READ_SEARCH_TOOLS = {"read_file", "search_files"}
 
 
 def handle_function_call(
@@ -305,7 +306,6 @@ def handle_function_call(
     """
     # Notify the read-loop tracker when a non-read/search tool runs,
     # so the *consecutive* counter resets (reads after other work are fine).
-    _READ_SEARCH_TOOLS = {"read_file", "search_files"}
     if function_name not in _READ_SEARCH_TOOLS:
         try:
             from tools.file_tools import notify_other_tool_call