feat: session_search tool + tool expansion docs update

session_search (tools/files.py):
- Full-text search across past session logs, exposed to the orchestrator
- Params: query (required), limit (default 5, max 20)
- Returns dated excerpts, newest first; own sessions only via ContextVars
- User-level — no TOOL_ROLES gating needed
- Registered in __init__.py callables + TOOL_CATEGORIES["Files"]

ARCH__FUTURE.md §2: updated tool count to 44, marked prior tools complete,
added Round 2 planned tools table (session_search now done, reminders due dates,
http_post, nc_talk_history, task_list priority filter, http_fetch max_chars),
noted datetime_now is not needed (already in system prompt via context_loader)

TODO__Agents.md: session_search checked off, Round 2 task list added

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/tools/__init__.py

@@ -30,7 +30,7 @@ from tools.ae_knowledge import (
     journal_entry_prepend as _ae_journal_entry_prepend,
 )
 from tools.ae_tasks import task_list as _ae_task_list
-from tools.files import file_read as _file_read, file_list as _file_list, file_write as _file_write
+from tools.files import file_read as _file_read, file_list as _file_list, file_write as _file_write, session_search as _session_search
 from tools.system import (
     shell_exec      as _shell_exec,
     claude_allow_dir as _claude_allow_dir,
@@ -89,7 +89,7 @@ import tools.agent_notes  as _mod_agent_notes
 
 TOOL_CATEGORIES: dict[str, list[str]] = {
     "Web":              ["web_search", "http_fetch"],
-    "Files":            ["file_read", "file_list", "file_write"],
+    "Files":            ["file_read", "file_list", "file_write", "session_search"],
     "Shell":            ["shell_exec", "claude_allow_dir"],
     "System":           ["cortex_restart", "cortex_logs", "cortex_status", "cortex_update"],
     "Tasks":            ["task_list", "task_create", "task_update", "task_complete"],
@@ -126,6 +126,7 @@ _CALLABLES: dict[str, callable] = {
     "file_read":                 _file_read,
     "file_list":                 _file_list,
     "file_write":                _file_write,
+    "session_search":            _session_search,
     "shell_exec":                _shell_exec,
     "claude_allow_dir":          _claude_allow_dir,
     "cortex_restart":            _cortex_restart,