Expose manage_notes via native function calling (#759)

The agent's RAG tool selector retrieves manage_notes as relevant for
note / todo / reminder requests, but two gaps stopped it from actually
firing on local llama.cpp / vLLM endpoints:

1. FUNCTION_TOOL_SCHEMAS had no entry for manage_notes. Even when the
   tool was marked relevant, no JSON schema was sent on the function
   tools list, so native-function-calling models had nothing to call.
   In practice the model would describe creating the note in prose
   while the actual note stayed blank — the symptom reported in #713
   ("checklist hallucinated as blank").

2. _API_HOSTS only listed hosted providers (OpenAI, Anthropic, etc.).
   For local endpoints like http://localhost:8080 or
   http://host.docker.internal:8000, _is_api_model fell back to
   keyword-sniffing the model name, so any model whose slug didn't
   happen to match the keyword list silently lost native tool
   schemas entirely.

Fixes:

- src/tool_schemas.py: add a manage_notes function schema covering
  list/add/update/delete/toggle_item with the full Keep-style field
  set. note_type is exposed as an enum ("note" | "checklist") so the
  model picks the mode explicitly instead of inferring it from
  content shape. Items are named checklist_items in the schema —
  consistent with the description's wording and avoiding the
  Python-built-in name clash that #713 calls out.

- src/tool_implementations.py: do_manage_notes accepts both
  checklist_items (new, schema-exposed) and items (legacy /
  internal). Direct API callers and existing code paths keep
  working unchanged; native function calls following the new
  schema route through the same path.

- src/agent_loop.py: add localhost, 127.0.0.1, and
  host.docker.internal to _API_HOSTS so the function-tool path is
  not gated behind model-name guessing for local servers.

Closes #174.
Closes #713.

src/tool_schemas.py

@@ -448,6 +448,41 @@ FUNCTION_TOOL_SCHEMAS = [
             }
         }
     },
+    {
+        "type": "function",
+        "function": {
+            "name": "manage_notes",
+            "description": "Manage notes and checklists (Google Keep-style): list, add, update, delete, toggle_item. IMPORTANT: For to-do lists / checklists, set note_type='checklist' and pass the items as the `checklist_items` array — do NOT serialize them into `content` as plain text. For freeform notes, use note_type='note' and put the body in `content`. `due_date` accepts natural language like 'tomorrow at 9am' (parsed in the user's timezone) and fires a notification — do not also create a calendar event for the same reminder.",
+            "parameters": {
+                "type": "object",
+                "properties": {
+                    "action": {"type": "string",
+                               "enum": ["list", "add", "update", "delete", "toggle_item"],
+                               "description": "The action to perform"},
+                    "id": {"type": "string", "description": "Note id (for update/delete/toggle_item); 8-char prefix is fine"},
+                    "title": {"type": "string", "description": "Note title (for add/update)"},
+                    "content": {"type": "string", "description": "Freeform body text. Use this for note_type='note'. Do NOT use this for checklists — pass `checklist_items` instead."},
+                    "note_type": {"type": "string", "enum": ["note", "checklist"],
+                                  "description": "'note' = freeform text in `content`. 'checklist' = structured to-do items in `checklist_items`. Defaults to 'checklist' if checklist_items is supplied, else 'note'."},
+                    "checklist_items": {"type": "array",
+                                        "items": {"type": "object",
+                                                  "properties": {
+                                                      "text": {"type": "string", "description": "The to-do item text"},
+                                                      "done": {"type": "boolean", "description": "Whether the item is checked off"}
+                                                  },
+                                                  "required": ["text"]},
+                                        "description": "Checklist items for note_type='checklist'. Each item is {text, done}. REQUIRED for checklists — leaving this empty produces a blank note."},
+                    "color": {"type": "string", "description": "Optional color label (e.g. 'yellow', 'blue', 'green')"},
+                    "label": {"type": "string", "description": "Optional category label (also used as a list filter)"},
+                    "pinned": {"type": "boolean", "description": "Pin the note to the top"},
+                    "archived": {"type": "boolean", "description": "For update: archive/unarchive. For list: show archived notes when true."},
+                    "due_date": {"type": "string", "description": "Reminder time. Accepts natural language ('tomorrow at 9am', '11pm today') or ISO 8601. Fires a notification at that time."},
+                    "index": {"type": "integer", "description": "Checklist item index (for toggle_item, 0-based)"}
+                },
+                "required": ["action"]
+            }
+        }
+    },
     {
         "type": "function",
         "function": {