ui: always show Global Arguments and drop the broken G toggle

[someson]

Problem

G (toggle the Global Arguments section) was a no-op in every configuration measured. With a fixture matching a real az command (7 globals):

Terminal	Globals visible?	G changes anything?
106x30	yes	no — fitAll forces them visible, so the toggle cannot hide them
106x12	no	no — hidden and unrevealable
106x5	no	no
80x30 (single-col)	no	no — and the view printed press G to show 4 global argument(s), advertising a key that did nothing

The key reached the handler and flipped showGlobals correctly; the rendering just never depended on it in a way the user could reach. gridLayout computed showAllGlobals := m.showGlobals || fitAll, and fitAll was true whenever the globals fit vertically — which is the common case.

Change

Globals always participate in the layout. Removed showGlobals, the G binding (including the dead ShowGlobal entry in keys.go), fitAll/showAllGlobals, hasHiddenGlobal, both press G hints, the ShowGlobals() accessor, the in-app help entry, and the README line.

Net −73 lines including a new test file.

Tests

• TestGlobalsAlwaysInLayout — asserts all 7 globals are in globalsCol at six terminal sizes (140x40 down to 80x10) and that no view mentions press G. The assertion is on the layout, not the rendered window: on a short terminal globals sit below the fold, which is ordinary scrolling rather than hiding.
• TestGlobalsRenderWhenRoom — the visible counterpart on a roomy terminal.
• TestFormShowGlobalsToggle deleted (behaviour gone). TestShowGlobalsMovedToShiftG reduced to TestLowercaseGOpensSetVarPopup, keeping the half that still matters: g must open the set-var popup.
• makeGridForm lost its showGlobals parameter across 11 call sites.

Full suite, go vet, gofmt and golangci-lint all clean locally, with the e2e tests genuinely executing (internal/ui 61s, not the ~1.4s that means they skipped).

Note

The keys.go diff is large because gofmt realigned both blocks after ShowGlobal — the longest field name — was removed. Only two lines are semantic.