The bag has MP in it and the harness cannot see it: no MP restorative in fieldCare, and the route never buys one

[mtklein]

Surfaced by the #228 lab, and it is a supply question rather than a bug.

H.fieldCare knows exactly six items — Tonic, Potion, Fenix Down, Antidote, Soft, Remedy — and no MP restorative at all. Meanwhile:

• The bag at the Narshe defense already holds 2 Elixirs (usable anywhere, full HP and MP) that nothing in the harness will ever reach for. The 3 Sleeping Bags and 2 Tents beside them are save-point-only and genuinely unusable mid-descent, but the Elixirs are not.
• There is no Tincture in the bag, and the two shops the route asserts — South Figaro 8, Narshe 15 — do not stock one. But Figaro Castle's item shop does, at 1500 gil for 50 MP, and gen_edgar.lua stops there and buys only Tonics.

This matters more now than it did before #219. The owner's supply guideline is a band of consumables carried by level (~level×5 Tonics, ~level Fenix), and that band was written when MP was spent only on casts. With boosted abilities priced, MP is a consumable the party spends every fight and has no way to restock between save points — which is precisely the squeeze #228 measured: 87 max MP buying two boosted crossbows across a seven-battle segment with no refill point.

Worth deciding together rather than piecemeal:

1. Should fieldCare learn an MP restorative, and on what threshold? It would need the same care as HP — an MP band rather than a top-up-to-full — or the party will drink Elixirs on a 1-MP deficit.
2. Should the route buy Tinctures where they are sold, and should the supply band gain an MP column?
3. Elixirs are scarce and irreplaceable; a rule that spends them freely is worse than one that never touches them. "In battle when a caster is dry and the fight is still live" is probably the honest shape, which makes it a fight-driver decision, not a field one.

Related: #228 (the descent), docs/design/mp-economy.md (which names Item as the channel refills arrive through, but the harness has never had one).

[mtklein]

Scope note from wt/field-lib: field care now knows a Zombie cure (Revivify, $F1), but no generator buys Revivify -- the route only ever holds the two that thamasa_night happens to carry. Shops on the route that stock it: 22 Jidoor, 24 Albrook, 35 Thamasa, 31 Vector area. When the supply band gains its MP column, add a small Revivify line (~3, at Albrook or Thamasa) so the cure is live on the route and not only on the bag's leftovers.

[mtklein]

Owner ruling (2026-09-21): Tinctures and Elixirs are Tonic/Potion analogues one level rarer -- a Tincture is costed like a Potion, an Elixir above that. Field care should learn Tinctures and Elixirs the way it knows healing items, AND reason about Tents and Inns, which restore both resources: there is a cost-benefit analysis to do among health-only, MP-only, tent and inn. In progress on wt/mp-supply: a short design section with the measured prices and the rule for each, the supply band gaining an MP column, the route buying Tinctures where sold, and field care learning the MP band and tent/inn use. Elixirs stay out of field care (a dry caster mid-fight is the fight driver's call).