feat(notes): add_note MCP tool with a per-day agent cap

Agents can write into the user's daily notes, but only within limits:
max 10 agent notes a day, max 500 characters, add only — no edit, no
delete. A new from_agent column separates their lines from the user's
so the cap counts the right ones and the UI can mark them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ClaudeDo.Data/Migrations/20260828185839_AddDailyNoteFromAgent.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ClaudeDo.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddDailyNoteFromAgent : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "from_agent",
+                table: "daily_notes",
+                type: "INTEGER",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "from_agent",
+                table: "daily_notes");
+        }
+    }
+}