Made training gather materials, fixed the trade graph, and banked money gifts

Unit orders now gather steel and high-tech over the days before training, exactly as buildings do, and clicking a queued order reveals what it is gathering, its reserved budget and the soldiers it will draw.

The trade graph cached a producer-less node list under a stamp that already reflected the producers' stores, so every seeded mine stayed invisible to buyers and rare-good prices settled at a huge multiple of base; the storage nodes are now re-read after production.

Money gifts draw the giver's central-bank reserves in the denomination first, buy the rest from the issuing bank at the market rate, convert into the receiver's currency, and cannot buy from a bank their nation is at war with.

Pruned the finished design briefs (intelligence, stacks, air movement, politics performance, economy balance, training UI and FIXME) and refreshed the index and cross-references.

SIMPLIFICATIONS.md

@@ -99,23 +99,7 @@ uses a nominal two-tile road delivery.*
 - Files: `shared/game_state/resources.js`, `shared/game_state/economy.js`,
   `client/js/map_view/modes.js` (delivery graph), `client/js/map_view/economic.js`.
 
-## 6. Give-money treaties bypass FX and reserves
-
-**`[~]`** *Give money is denominated in any currency but (simplified) the sum
-moves straight between the two treasuries, with no FX or central-bank reserve
-leg.*
-
-- Today: `shared/game_state/treaties.js` moves the sum directly; the
-  "cannot get currency from a central bank at war with you" rule is not
-  modelled.
-- Full model: draw from the giver's foreign reserves, otherwise buy from the
-  relevant central bank at the market rate; block a bank whose nation is at war.
-- Questions: which FX rate and spread? Does a reserve shortage fail the treaty
-  or partially settle?
-- Files: `shared/game_state/treaties.js`, `shared/game_state/` currency/central
-  bank mixins, `client/js/modals/nation.js` (treaty compose).
-
-## 7. Missiles / WMD
+## 6. Missiles / WMD
 
 **`[~]`** *Missiles* and *WMDs* are marked `[~]` while their sub-items are
 largely `[x]`.
@@ -125,15 +109,14 @@ largely `[x]`.
   design and needs `nuclear_weapons` + `space_program`. A nuclear blast kills
   ~90% of a tile's people, destroys buildings/improvements except bunkers and
   fortifications, and costs every nation popularity.
-- What is unfinished: the WMD follow-up "foreign intelligence may be warned that
-  you are enriching uranium" (see `INTELLIGENCE.md`), and any further
-  refinement of blast falloff / interception.
+- What is unfinished: further refinement of blast falloff / interception (the
+  "foreign intelligence may be warned that you are enriching uranium" follow-up
+  is now implemented).
 - Files: `shared/game_state/wmd.js`, `shared/data/units.js`,
   `shared/data/combat.js`, `client/js/game_screen/panels.js`.
 
 ---
 
-## 8. Related design docs
+## 7. Related design docs
 
-`DESIGN.md` (index), `INTELLIGENCE.md`, `STACKS.md`, `AIR_MOVEMENT.md`,
-`ECONOMY_BALANCE.md`, `POLITICS_PERFORMANCE.md`, `TRAINING_UI.md`, `ICONS.md`.
+`DESIGN.md` (index), `ICONS.md`.