Docs for strangers: real quick start, own-shelves guide, clone-safe stub guard

README rewritten for a fresh clone: working status, quick start with
env-var table and per-stage commands, photo-taking guidance, a
bring-your-own-shelves section (this repo carries the author's live
data), tokenless workflows, and a dev section. New committed
data/STUB_DATA.marker closes a real gap: the cache marker is
gitignored, so a fresh clone had stub-derived to_add.csv with no
guard — upload now refuses on either marker. Username docs: BGG_USERNAME
in .env is the one place it's needed; config.toml is a fallback.

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

config.toml

@@ -1,9 +1,12 @@
 # Non-secret configuration for bggpipe. Secrets (ANTHROPIC_API_KEY,
-# BGG_PASSWORD) come from env vars only and must never appear here.
+# BGG_PASSWORD, BGG_API_TOKEN) come from env vars only and must never
+# appear here.
 
-# TODO(eric): set your BGG username — the live smoke test and diff/upload
-# stages need it. Leave empty to skip the live smoke test.
-bgg_username = ""
+# The BGG username isn't a secret (it's public on your profile), so it may
+# live here — but BGG_USERNAME from .env OVERRIDES it, and since upload
+# needs BGG_USERNAME anyway, .env alone is enough. Cloners: change or
+# clear this.
+bgg_username = "ewagoner"
 
 photos_dir = "photos"
 data_dir = "data"