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>

agent/context_compressor.py

@@ -45,16 +45,18 @@ class ContextCompressor:
         quiet_mode: bool = False,
         summary_model_override: str = None,
         base_url: str = "",
+        api_key: str = "",
     ):
         self.model = model
         self.base_url = base_url
+        self.api_key = api_key
         self.threshold_percent = threshold_percent
         self.protect_first_n = protect_first_n
         self.protect_last_n = protect_last_n
         self.summary_target_tokens = summary_target_tokens
         self.quiet_mode = quiet_mode
 
-        self.context_length = get_model_context_length(model, base_url=base_url)
+        self.context_length = get_model_context_length(model, base_url=base_url, api_key=api_key)
         self.threshold_tokens = int(self.context_length * threshold_percent)
         self.compression_count = 0
         self._context_probed = False  # True after a step-down from context error