refactor: split tool declarations into domain files + role config UI

tools/__init__.py shrinks from 1,137 → 250 lines. Each domain file now
owns both its callables and its FunctionDeclarations (DECLARATIONS list),
so adding a new tool only touches one file.

New TOOL_CATEGORIES dict exported from __init__ — used by the UI for
grouped tool checkboxes.

Role config UI (Settings → Model Registry → Role Assignments):
- ⚙ button per role expands an inline configure panel
- Textarea for system_append (injected into system prompt for this role)
- Grouped checkboxes for tool allow-list (all checked = no restriction)
- POST /api/models/role-config saves both fields; updates ROLE_CONFIG_DATA
  in-page so re-open reflects current state without a page reload

Backend:
- model_registry.set_role_config() writes system_append + tools to registry
- TOOL_CATEGORIES exported from tools/__init__ for UI rendering
- TOOLS.md header updated: 30 → 39 tools (ae_journal_* and cortex_* additions)

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

cortex/tools/scratch.py

@@ -17,6 +17,7 @@ import asyncio
 from datetime import datetime, timezone
 from pathlib import Path
 
+from google.genai import types
 from persona import persona_path
 
 
@@ -77,3 +78,51 @@ async def scratch_append(content: str, heading: str | None = None) -> str:
 
 async def scratch_clear() -> str:
     return await asyncio.to_thread(_scratch_clear)
+
+
+DECLARATIONS = [
+    types.FunctionDeclaration(
+        name="scratch_read",
+        description=(
+            "Read the full contents of the scratchpad. "
+            "Use this to recall working notes, mid-task context, or anything previously jotted down. "
+            "The scratchpad is transient — nothing here is distilled or archived."
+        ),
+        parameters=types.Schema(type=types.Type.OBJECT, properties={}),
+    ),
+    types.FunctionDeclaration(
+        name="scratch_write",
+        description=(
+            "Replace the entire scratchpad with new content. "
+            "Use this to set a clean working note, replacing whatever was there before. "
+            "For adding without replacing, use scratch_append instead."
+        ),
+        parameters=types.Schema(
+            type=types.Type.OBJECT,
+            properties={
+                "content": types.Schema(type=types.Type.STRING, description="The new scratchpad content (markdown supported)"),
+            },
+            required=["content"],
+        ),
+    ),
+    types.FunctionDeclaration(
+        name="scratch_append",
+        description=(
+            "Add a new section to the bottom of the scratchpad without replacing existing content. "
+            "Each section gets a timestamp heading unless you supply one."
+        ),
+        parameters=types.Schema(
+            type=types.Type.OBJECT,
+            properties={
+                "content": types.Schema(type=types.Type.STRING, description="The content to append (markdown supported)"),
+                "heading": types.Schema(type=types.Type.STRING, description="Optional section heading. Defaults to current UTC timestamp."),
+            },
+            required=["content"],
+        ),
+    ),
+    types.FunctionDeclaration(
+        name="scratch_clear",
+        description="Erase everything in the scratchpad. Use when the working notes are no longer needed.",
+        parameters=types.Schema(type=types.Type.OBJECT, properties={}),
+    ),
+]