Offer the simulator one input per metric, not one per source

[freethinkel]

The Simulator panel listed one input per data source, and the firmware answers many ids out of one
metric — steps alone covers eight (0x19, 0x25, 0x26, 0x49, 0x6a, 0x6c, 0x6f, 0x82, all
Number(sim.steps) in idValue). So Combo showed a Steps field, a Steps goal field, and
three more inputs — steps (slot) (0x26), (0x49), (0x6c) — for the same number. Worse, a value
typed in one of those wins over the field above (idValue reads sim.overrides[id] first) with
nothing in the UI saying so.

On top of that the grid was a fixed list of eleven metrics regardless of the document: Combo has no
AQI, temperature or distance widget and got fields for all three.

After

The grid is derived from what the open document reads, each metric with its goal beside it. Combo
goes from eleven fields to three:

before	after
Steps · HR · Battery · Calories · Distance · Temp · AQI · Stand hours · Steps goal · Cal goal · Stand goal, then 9 per-id rows	Steps · Steps goal · Battery, then a folded per-source overrides

The per-id inputs are still there — they are the only way to drive two widgets on one metric apart,
or to pin a hand — but inside a <details> whose summary counts how many are set, so a shadowing
override is visible instead of silent.

Where the mapping lives

Which metric an id reads was implicit in idValue's switch and duplicated as hint strings in the
panel ("0x19, 0x26, 0x49, 0x6a, 0x6c"). It is now the ID_METRIC table, which idValue itself
reads for every source that is a plain passthrough; the derived ones (distance's km/mi, integer and
fraction splits) still compute in the switch and are listed only so the panel can group them.
tests/sim-sources.test.ts asserts per id that the two agree — each mapped id must move when, and
only when, the metric the panel files it under moves.

Also

/max was the widget's declared max (meta.max — a hand's 60 positions, a number's digit cap),
not the metric's range, which is why the panel offered "day of month /60". It reads max 60
now, with a title saying whose max it is.

Verification

pnpm check 0 errors, pnpm lint clean, oxfmt --check clean, 185 tests pass (24 new). Checked in
a real browser against Combo: three fields, the fold opens to the nine sources, typing 999 into
steps (slot) (0x26) flips the summary to "per-source overrides — 1 set".

(The first commit is the same format:check fix as #25 — frame-thumb.svelte is unformatted on
main, so CI is red there for both branches until either lands.)

🤖 Generated with Claude Code

https://claude.ai/code/session_01QLHPEnYV5UMkne4WBTCk5s