fix(docs): open v0.1 working file from /sd/repo not /sd/local

The product doc opened notes.md from /sd/local, the permanently-private
scope where Publish is unavailable — contradicting the headline Ctrl-G
flow and every other doc. Point it at the Tracked working copy.

docs/v0.1-mvp-product.md

@@ -52,11 +52,11 @@ at build time:
   a `.env` file gitignored locally) and embedded as `const &'static str`s in
   the binary.
 - The dev clones the git working copy onto the SD card from their laptop
-  (`git clone` directly onto the mounted SD), so `/sd/local/notes.md` is
+  (`git clone` directly onto the mounted SD), so `/sd/repo/notes.md` is
   present at first boot.
 - Re-configuring = re-build + re-flash. For a single-dev MVP, that's fine.
 
-If the firmware boots and finds no `/sd/local` or no `/sd/local/notes.md`, it
+If the firmware boots and finds no `/sd/repo` or no `/sd/repo/notes.md`, it
 shows a one-line error on the splash and stops. No recovery flow ships in
 v0.1 — the dev re-mounts the SD and reboots.
 
@@ -75,7 +75,7 @@ Auth model rationale: [ADR-005](adr.md#adr-005-auth--https--github-personal-acce
   Boot (~3 s): Wi-Fi stays off (brought up on demand by `Ctrl-G`)
         │
         ▼
-  Open /sd/local/notes.md, place cursor at end of file
+  Open /sd/repo/notes.md, place cursor at end of file
         │
         ▼
   [EDITING] ← keypresses, partial refresh per edit