refactor(tools): collapse tool_implementations to clean re-export shim

Move shared _INTERNAL_BASE/_internal_headers to src/tools/_common.py and
drop the duplicate _parse_tool_args (already in _common). tool_implementations.py
is now a pure re-export facade (+ 3 pre-existing email-context helpers, out of
scope). Domain files' function-local imports of these names still resolve via
the facade re-export.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/tools/_common.py

@@ -4,6 +4,9 @@ Extracted from tool_implementations.py as part of slice 1 (#4082/#4071).
 Domain modules under src/tools/ import from here.
 """
 import json
+from typing import Dict, Optional
+
+from core.constants import internal_api_base
 
 
 def _parse_tool_args(content):
@@ -37,3 +40,19 @@ def _parse_tool_args(content):
     ):
         args = args["body"]
     return args
+
+
+# In-process loopback base for agent tools that call Odysseus's own API
+# (cookbook state, model serve, gallery, email, calendar). We ride the
+# per-process internal token so require_admin lets us through. See
+# core/middleware.py. Resolution (override / APP_PORT / 7000) lives in
+# core.constants.internal_api_base().
+_INTERNAL_BASE = internal_api_base()
+
+
+def _internal_headers(owner: Optional[str] = None) -> Dict[str, str]:
+    from core.middleware import INTERNAL_TOOL_HEADER, INTERNAL_TOOL_TOKEN
+    headers = {INTERNAL_TOOL_HEADER: INTERNAL_TOOL_TOKEN}
+    if owner:
+        headers["X-Odysseus-Owner"] = owner
+    return headers