fix(exceptions): correct AdagentsAccessBlockedError suggestion text and add publisher_domain attr

- Replace wrong function name fetch_agent_authorizations_from_directory()
  with fetch_agent_authorizations() (correct public API)
- Replace "buyers" terminology with "SDK callers" (domain-neutral)
- Add self.publisher_domain attribute so err.publisher_domain is accessible
- Tighten suggestion prose: remove AAO qualifier (function already implies it)

Refs #801

Author: bokelley

src/adcp/exceptions.py

@@ -288,31 +288,31 @@ def __init__(self, publisher_domain: str, timeout: float):
 class AdagentsAccessBlockedError(AdagentsValidationError):
     """adagents.json fetch blocked by publisher-side bot management (403, cf-mitigated: challenge).
 
-    Only surfaces in direct-fetch workflows (``fetch_adagents``). Production
-    buyers that use ``fetch_agent_authorizations_from_directory`` bypass
-    publisher-side bot management entirely — the AAO directory crawler handles
-    publisher fetches and serves cached results.
+    Only surfaces in direct-fetch workflows (``fetch_adagents``). SDK callers that
+    use ``fetch_agent_authorizations`` avoid this entirely — the AAO directory crawler
+    handles publisher fetches and serves cached results without exposing the SDK to
+    publisher-side bot management.
 
     If you need to catch this specifically without catching all
     ``AdagentsValidationError``s, use ``except AdagentsAccessBlockedError``.
     """
 
     def __init__(self, publisher_domain: str):
         """Initialize bot-management blocked error."""
+        self.publisher_domain = publisher_domain
         message = (
             f"adagents.json blocked by bot management for {publisher_domain} "
             f"(HTTP 403, cf-mitigated: challenge)"
         )
         suggestion = (
             "The publisher's origin blocked this request with a Cloudflare bot management\n"
-            "     challenge. This only affects direct adagents.json fetches; production\n"
-            "     buyers use the directory API which bypasses publisher-side bot management.\n"
+            "     challenge. This only affects direct adagents.json fetches (fetch_adagents).\n"
             "\n"
             "     To unblock local debugging:\n"
             "     - Retry with a browser-like User-Agent via the user_agent= parameter, e.g.\n"
             '       user_agent="Mozilla/5.0"\n'
-            "     - Or use fetch_agent_authorizations_from_directory() to query via the\n"
-            "       AAO directory instead of fetching publisher adagents.json directly."
+            "     - Or call fetch_agent_authorizations() to query the AAO directory instead,\n"
+            "       which bypasses publisher-side bot management entirely."
         )
         super().__init__(message, None, None, suggestion)