watched: single DONE_RATIO source constant replaces the seven hardcoded 0.95 literals

server/app.py DONE_RATIO is injected into index.html like {{VERSION}}, app.js
reads it as window.DONE_RATIO (fallback = same default). Change the threshold
in exactly one place now.

server/app.py

@@ -44,6 +44,11 @@ def _version():
 
 VERSION = _version()
 
+# An episode counts as "watched" once you're this far through it (fraction of
+# duration). One knob for client + server: injected into index.html below so
+# app.js uses the same value as these stats. Change here only.
+DONE_RATIO = 0.95
+
 # latest probe result + last 20 samples (~1h at 3-min spacing), for GET /api/cdn
 _CDN = {"state": "unknown", "kbps": 0.0, "ts": 0.0, "hist": []}
 # origin (primary provider pages/API) health — separate host, separate failure
@@ -455,7 +460,7 @@ def api_stats(request: Request, days: int = Query(30, ge=1, le=365),
         if s["last_ts"] > a["last_seen"]:
             a["last_seen"] = s["last_ts"]
             a["cur_ep"] = s["last_ep"]
-        if s["dur"] > 0 and s["max"] >= s["dur"] * 0.95:
+        if s["dur"] > 0 and s["max"] >= s["dur"] * DONE_RATIO:
             a["completed"] += 1
             completed += 1
     now = time.time()
@@ -700,8 +705,10 @@ def stream(token: str):
 @app.get("/index.html", include_in_schema=False)
 def index():
     # index.html is served (not mounted) so ?v={{VERSION}} becomes the git
-    # SHA at startup; other statics go through the mount below
-    return HTMLResponse(_INDEX_HTML.replace("{{VERSION}}", VERSION))
+    # SHA and {{DONE_RATIO}} the watched threshold at startup; other statics
+    # go through the mount below
+    return HTMLResponse(_INDEX_HTML.replace("{{VERSION}}", VERSION)
+                        .replace("{{DONE_RATIO}}", repr(DONE_RATIO)))
 
 
 _INDEX_HTML = (ROOT / "static" / "index.html").read_text()