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]>

CLAUDE.md

@@ -201,9 +201,10 @@ event's length. It adds **no schema field**, so the feed contract is untouched.
   claims. A source quietly moving a date must not erase a fortnight's streak that exists nowhere
   else.
 - **Detection is a default, not a verdict.** The reader can mark any event as repeating, or unmark
-  one detection got wrong (`progress.daily`, resolved by `resolveDaily`). Store an override only
-  when it *disagrees* with detection — recording agreement would freeze today's guess and stop a
-  better parser from ever reaching that event.
+  one detection got wrong (`progress.daily`, resolved by `resolveDaily`), and `prefs.detectDaily`
+  switches the guessing off entirely. Store an override only when it *disagrees* with detection —
+  recording agreement would freeze today's guess and stop a better parser from ever reaching that
+  event. Neither control ever deletes a mark or a logged day, so both are reversible.
 
 ## Conventions