feat: let the reader switch off daily detection

Guessing from a source's wording is right most of the time, and someone
who finds it wrong often enough should be able to stop it rather than
dismiss the same false positive every patch.

Off, only events the reader marked themselves get a checklist. It
silences the guess rather than deleting anything: overrides, ticks and
streaks all survive, so switching it back on restores exactly what was
there. With it off, marking an event stores an explicit yes, since there
is no longer a detection for an override to agree with.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

docs/DATA-MODEL.md

@@ -199,8 +199,8 @@ Namespaced, versioned, and small. Nothing here ever goes to the server.
 "gacha-tracker:v1:progress"     // { [eventId]: { status?, effort?, note?, at } }
 "gacha-tracker:v1:daily"        // { [id]: { days: ["2026-08-15", ...], at } }
 "gacha-tracker:v1:ignored"      // { [eventId]: { at } }  — "stop showing me this"
-"gacha-tracker:v1:prefs"        // { region, hiddenGames[], sort, showCompleted, showIgnored,
-                                //   regionConfirmed, onboarded }
+"gacha-tracker:v1:prefs"        // { region, hiddenGames[], sort, detectDaily, showCompleted,
+                                //   showIgnored, regionConfirmed, onboarded }
 "gacha-tracker:v1:completions"  // SUPERSEDED — read once to migrate, never written
 ```
 
@@ -257,8 +257,11 @@ Dailiness is derived from the published event — `type: "login"`, or wording li
 "check-in", "7-day" in the title or summary — and never from a game's habits or an event's length.
 It adds no schema field, so nothing about the feed contract or the event ID changes.
 
-**The reader overrules detection.** `progress.daily` records their answer and wins outright
-(`resolveDaily`); absent means they have not said, so detection stands. An override that merely
+**The reader overrules detection**, per event and globally. `progress.daily` records their answer
+for one event and wins outright (`resolveDaily`); absent means they have not said, so detection
+stands. `prefs.detectDaily` switches the guessing off altogether, leaving only events they marked
+themselves — it silences detection rather than deleting anything, so every mark and every logged day
+survives and switching it back on restores exactly what was there. An override that merely
 agrees with detection is **not stored** (`dailyOverride`) — freezing today's guess into their data
 would stop a later parser improvement from ever reaching that event. This is the only field in
 `progress` that changes what the app *shows* rather than recording what the reader did, which is