feat(score): compute a health score from the data a person actually has

Three distinct areas of health stops being the price of admission and
becomes what it always described: a recommendation. `evaluateScoreBreadth`
returns a tier instead of a pass/fail — `full` at three areas or more,
`partial` at two, `minimal` at one — and refuses only when not one pillar
came back usable, with the reason `no_usable_data`.

The arithmetic does not change with the tier. Same mean, same worst-pillar
band drag, same noise floor. A one-area score of 82 is an honest 82 that
rests on one area, and discounting it for the pillars somebody does not
track would have been a new invented target, which is the thing this score
spent two releases removing.

The physiological requirement becomes a labelling fact rather than a veto.
An account whose only readable pillar is activity or wellbeing gets its
number with `physiological: false` on the basis block; the old refusal told
that person nothing they could not already see.

`SCORE_MIN_ELIGIBLE_DOMAINS` is now `SCORE_RECOMMENDED_DOMAINS` and still
feeds `deriveCoverage`, so the coverage fraction and the confidence blend
keep telling the truth with no new machinery: a one-area score lands at low
confidence through the path that was already there. The fraction used to be
a floor every scored account had cleared; it is a real moving number now.

`SCORE_VERSION` 3 -> 4 and `SCORE_ALGORITHM_CHANGED_AT` moves to the
release date. Both are method-identity duties: deltas suppress as
`algorithm_changed` across the straddle window, the notice key rotates so
each account is told once, and stored days stamp 4. No v3 row is rewritten
and no v3 number changes meaning.

The settings write follows the same rule rather than a stricter one. It
refused two-area and non-physiological selections on the ground that they
could not produce a score; they can, so refusing the write would be the two
layers disagreeing about the one question they share. The empty selection
is still refused, under a single reason `no_pillars_selected`, and the seven
message catalogues trade the two old refusal sentences for one.

Also fixes the stale `./series.ts` reference in the config header — that
module was deleted as dead in v1.35; the columns the sentence describes are
still written by `./record.ts`.

src/app/api/auth/me/health-score-config/route.ts

@@ -19,15 +19,17 @@
  *
  * Two things this route is responsible for beyond storing a list.
  *
- * **It refuses a selection that cannot produce a score.** Three distinct
- * areas of health and at least one physical measurement, or the
- * composite does not exist. Saving such a selection would leave the
- * person with a settings page that says one thing and a score that has
- * silently vanished, so the write is refused with a sentence they can
- * act on. The scorer applies the same rule again at read time through
- * the same function, deliberately: a config written before a rule change
- * or edited outside the app still meets an honest refusal rather than a
- * missing number.
+ * **It refuses a selection that cannot produce a score.** As of v1.38
+ * that is one selection: the empty one. Three areas of health is what
+ * the score recommends, not what it demands — a two-area or one-area
+ * recipe now saves and produces a score that says on its face how broad
+ * it is, so refusing the write would refuse something the scorer is
+ * perfectly willing to compute. Taking every pillar out is different in
+ * kind: there is nothing left to average, and storing that recipe would
+ * leave the person with a settings page that says one thing and a score
+ * that has silently vanished. The scorer applies the same rule again at
+ * read time through the same function, deliberately, so a config edited
+ * outside the app meets an honest refusal rather than a missing number.
  *
  * **It evicts the score caches.** The person just changed what the
  * number means; serving the old one for the next hour would make the
@@ -82,14 +84,11 @@ const healthScoreConfigPatchSchema = z
 
 /**
  * Why a selection cannot produce a score, said the way a person would
- * say it. The cardiometabolic sentence is the one that surprises people:
- * blood pressure, glucose and cholesterol are three pillars but one area.
+ * say it. One entry, because one selection cannot: the empty one.
  */
 const BREADTH_REFUSAL = {
-  measured_physiological_domain_required:
-    "A health score needs at least one physical measurement. Keep one of blood pressure, glucose, sleep, body shape or cholesterol in your selection, alongside whatever else you choose.",
-  three_domains_required:
-    "A health score needs at least three different areas of health. Blood pressure, glucose and cholesterol all describe the same area, so a selection made only of those counts as one.",
+  no_pillars_selected:
+    "A health score needs at least one area of health to score. Keep one selected — the score will say which areas it is built from.",
 } as const;
 
 export const GET = apiHandler(async () => {