docs(persistence): note boot-load and :w/:sync save are wired

docs/v0.1-mvp-technical.md

@@ -175,6 +175,14 @@ hardware-verified 2026-07-11.
 - The file is read fully into the rope at boot. v0.1 caps file size at
   256 KB; larger files refuse to open with a clear message. Saving is not
   capped — the buffer is always persistable.
+- **Wired into `main.rs`** (2026-07-11): the editor boot-loads the note via
+  `Editor::with_text(Storage::load())` — a missing card / repo / unreadable note
+  halts boot with the reason painted on the panel — and `:w`/`:sync` persist
+  through `Storage::save`, inline on the UI loop (a small-file write is tens of
+  ms). Save errors are logged and the RAM buffer kept, so a card pulled
+  mid-session doesn't lose work. The git-push half of `:sync` is **not** wired
+  yet: it awaits `git_sync` being graduated into a module and run on the
+  dedicated git thread (see `git` below), so `:sync` currently just saves.
 
 ### `wifi` — on-demand station