Fan funding: the artist chooses the campaign goal in fans

The goal is no longer fixed at the larger of the plant minimum and the
break-even; that is now the floor, and the artist sets any goal above it.

- make-a-record.html: "Goal: how many fans you need" with number input,
  slider and chips (Lowest, 150, 200, 300, 500, 1,000); chips below the
  floor or above the edition cap stay visible but disabled with the
  reason; the goal also shows as the pre-order amount (fans x fan price);
  typing below the floor snaps back with a note; the campaign, the
  outcome and the stage run against the chosen goal; the tour shows the
  goal being raised to 150
- artist-order.html: goal field in the campaign card, same floor rule
- artist-platform.md: the floor rule and that a higher goal is all or
  nothing as well

Defaults unchanged (goal 100 = the plant minimum at 1,200 THB, break-even
41, 548 THB kept a copy).

docs/artist-platform.md

@@ -245,7 +245,8 @@ Nothing goes in front of fans that the plant cannot make:
 
 ### The goal
 
-The goal is the larger of two numbers:
+The artist sets the goal in fans. The lowest it can go is the larger of
+two numbers:
 
 - **the plant's minimum campaign run**, set by setup and stamper
   economics on the semi-automatic line (**100 copies** as a planning
@@ -253,10 +254,16 @@ The goal is the larger of two numbers:
 - **the artist's break-even**: the copies at which the fan price covers
   the per-title costs, the per-copy costs and the payment fees.
 
+Above that floor the goal is the artist's choice, for example a bigger
+first run or a round number to tell fans. A higher goal is all or nothing
+as well: if it is missed, every fan is refunded, even when the floor was
+passed. Both demos let the artist set it, with the goal shown in fans and
+as the pre-order amount (fans × fan price).
+
 With the illustration above and a fan price of 1,200 THB (an example,
 not a recommendation) and payment fees of about 3.5%: break-even is
-38,000 / (1,200 − 42 − 232) ≈ **41 copies**, so the goal is the 100-copy
-minimum. At 100 copies the artist keeps about **546 THB a copy**, at 300
+38,000 / (1,200 − 42 − 232) ≈ **41 copies**, so the lowest goal is the
+100-copy minimum. At 100 copies the artist keeps about **546 THB a copy**, at 300
 about **799 THB**, because the per-title cost spreads. The calculator
 shows the artist this before launch, for any price they type in. Shipping
 is charged to the fan separately at checkout, at cost.