docs: slim README to what it uniquely owns (run, features, dev commands); implementation detail already lived in SPEC.md — moved the two stragglers (anidb self-check, cache-busting) over

SPEC.md

@@ -124,6 +124,10 @@ across parallel byte-range lanes (single-stream fallback).
 Views: home (continue watching), search, detail+player, full history
 (`?history`), stats (`?stats`); PWA-installable.
 
+Cache-busting: the server injects the git SHA as `?v=` on
+`app.js`/`style.css` at startup (index.html itself is `no-store`), so
+a restart is a cache bump — nothing to hand-bump.
+
 - Default play: opening an anime resumes the last watched episode of
   the season (seeking to the saved position unless ≥95% through),
   else autoplays episode 1. If the browser blocks autoplay, the native
@@ -143,6 +147,10 @@ Use the app through your HTTPS proxy (with `Secure` cookies, plain
 remote HTTP can't hold a session). `.venv/bin/pytest tests/ -q` runs
 the hermetic suite against a throwaway server on :8399; the
 live-upstream browser e2e is opt-in (`ANIWEB_LIVE_TESTS=1`).
+`ANI_SOURCE=anidb .venv/bin/python -m server.upstream` runs a live
+self-check of the anidb fetchers (search → details → episodes → dub
+stream); must be the `-m` form (plain script execution breaks the
+providers' relative imports).
 
 ## Out of scope (v1)