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/ClaudeDoDbContextModelSnapshot.cs

@@ -205,6 +205,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("note_date");
 
+                    b.Property<bool>("FromAgent")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("from_agent");
+
                     b.Property<int>("SortOrder")
                         .HasColumnType("INTEGER")
                         .HasColumnName("sort_order");