fix(routines): test the copy, name what Yes agrees to, and true up the docs

Make it mine's copying was inline in App and untested; it is now a pure
function with a test, so a change to either store can't make the copy
silently arrive empty. The question's buttons now say what they answer
when heard out of context. The prefs block and the spec now match what
shipped.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/superpowers/specs/2026-10-13-periodic-tasks-design.md

@@ -133,12 +133,14 @@ Monday; monthly to the 1st.
   number is visibly dated rather than presented as current.
 - **Asking.** When a game with built-ins becomes visible — first-run picker, or switched on
   in settings — and is not in `routinesAsked`, a one-line card at the top of the dailies
-  strip asks: `Track Zenless Zone Zero's weekly and monthly tasks? Yes · No thanks`. Either
+  strip asks: `Track Zenless Zone Zero's built-in weekly tasks? Yes · No thanks`. Either
   answer records the game in `routinesAsked`; Yes also adds it to `routineGames`. Never a
   modal, and never asked twice.
-- **Toggle.** The games settings group shows a “Weekly tasks” switch on each game that has
-  built-ins, writing `routineGames`. Off hides the chips; their ticks and amounts stay.
-- **Make it mine.** From a built-in chip's editor or the settings list: copies the template
+- **Toggle.** *What you see* shows a “Built-in weekly tasks for <game>” switch, beside the daily
+  chores switch, for each game that has built-ins, writing `routineGames` (and answering the
+  strip's question). Off hides the chips; their ticks and amounts stay. Each built-in shows the
+  date its source gives (`asOf`), not the date we read it.
+- **Make it mine.** From the settings list: copies the template
   into a `mytask:` record with `from` set, and copies the built-in's ticks and amounts to
   the new id (additive; the originals stay). A built-in whose id is some task's `from` is
   hidden; deleting that copy brings it back.