feat: one brand identity across the apps and the icon

[Mr-Sunglasses]

Rebased onto the new main now that server/ is a submodule. The gateway WebUI
half of this work moved to VocaHQ/vocagateway#2; what is left here is the apps
and the icon.

The icon

Field keeps #0F6B57, the mark flips to near-white, and the outer arc pair is
dropped so the microphone can be drawn bigger. 2.98:1 → 5.90:1
mark-against-field, and it reads at 22px instead of turning into a smudge.
mark_box("both") still reproduces the measured 349×329 avatar reconstruction
exactly, so the provenance is intact.

(An earlier revision of this description, and of the icon commit's message, said
1.4:1 → 5.1:1. Those figures were estimated rather than computed. The numbers
above are measured, and generate.py --check now asserts the floor so the claim
cannot drift back to a guess.)

One identity

iOS was tinted system blue, the keyboard's resting accent was blue again, Android
used the brand green. BrandPalette now holds the two values for every target.

iOS	explanations move from List rows to Section footers — the reason the screens read as a column of slabs; SessionState.displayName replaces raw case names like uploadFailedRecoverable on the main screen
Android	SectionCard → Section, a heading and its content on the page instead of fourteen filled cards down Settings; interruptions become Notice and keep a container; Material's own button shape replaces a bespoke 16.dp corner that was on buttons, chips and cards

The floating bubble

It is a WindowManager overlay inflated from XML, so it could never read the
Compose ColorScheme — and nothing connected the two, so it sat in Material's
baseline purple (#4F378B on #1C1B1F) while the rest of the app was brand
green. Measured against its own chip that purple mic button was 1.83:1: the
primary control was the least visible thing on the overlay.

• res/values/colors.xml carries the palette entries the non-Compose world needs.
  The chip is our #1B1C1B dark surface at 95%; the mic is brand mint at
  9.32:1 against it.
• res/color/bubble_mic_icon.xml makes the glyph a state list, because the fill
  under it changes — dark ink on the mint idle fill, white on the red recording
  fill. The layout hardcoded white for both, which is 1.83:1 on mint.
• Recording moves off #B3261E (2.62:1 against the chip) to #E5484D (4.37:1).
  Deliberately not colorScheme.error — that pair is tuned for text on our own
  surfaces, not a fill on an overlay.

The bubble stays dark in both themes on purpose: it floats over other apps, so
one treatment that survives any background beats following a theme that has
nothing to do with the screen underneath.

Contrast bugs the blue was hiding

Every one of these would have shipped:

• SwiftUI .borderedProminent always draws a white label on the tint, which is
  1.7:1 on the dark palette's #77D0B2. Prominent buttons go through
  brandProminentButton() now.
• The keyboard's dictation bar hardcoded a white title on its accent fill, and
  every dark-appearance accent there is a light pastel, so all six states sat
  near 2:1.
• The helper that fixed that was itself wrong. It thresholded a luminance
  computed from gamma-encoded sRGB channels, and so picked the worse of the two
  options for three of the six dark accents — .listening scored 0.566 against a
  0.6 cut-off and took white at 2.65:1, where near-black was 6.93:1. It linearises
  and compares both candidates now. A disabled primary was also judged on its
  opaque colour while it draws at 55%, so light mode picked white on a fill that
  composites to ~#79ACA3.
• Removing Android's cards broke what they were propping up: on the white page a
  chip fill at #F4F5F3 was 1.09:1, and the pending setup-checklist icons
  were 1.76:1. Light containers and outline moved.
• The Compose schemes set surfaceVariant and surfaceContainerHigh but left the
  rest of the container ramp at Material's baseline — and NavigationBar reads
  surfaceContainer, ModalBottomSheet reads surfaceContainerLow. So the bottom
  bar on every screen and the language sheet were still purple-tinted
  #F3EDF7. Both ramps are set and monotonic now.

Checked against the shared org pack

VocaHQ/vocahq now carries a shared brand pack at web/assets/brand/. Our three
SVGs are identical to it (modulo aria-label): same #0F6B57 field, #F2F6F2
mark, #0B1A15 ink, same four arcs, same mark_box geometry. Its PNGs match its
own SVGs too.

Its -dark variants do not hold up: voca-logo-dark.svg and
voca-app-icon-dark.svg put the ink mark back on the brand field at 2.78:1 —
fractionally worse than the navy icon this work replaced. Our own dark handling is
unaffected (the iOS dark variant is a light mark on transparency, so the system's
dark field sits behind it), but the pack needs its own fix.

generate.py --check, wired into the root just ci, encodes the rules: 3:1 for
every mark against its ground, four arcs shipped, the six-arc reconstruction still
349×329, and the adaptive icon inside Android's visible circle.

Guards added

ColorPaletteTest	pins res/values/colors.xml to the Compose dark scheme and holds every bubble colour to a contrast floor, measured on the composited colours over a white app — the worst case for a 95% chip
DictationBarLabelColorTests	every accent takes the better of the two labels, in both appearances and both enabled states; enabled fills clear 3:1, the large-text threshold for a 14pt semibold label
generate.py --check	the brand rules above

ColorPaletteTest earned its keep on the first run by catching #00382A vs
#003827 between BrandPalette.swift and the Compose dark scheme; iOS is
corrected to the Android value.

Notes

• The generator no longer writes outside this repo. server/app/webui/favicon.svg
  was an ordinary SVGS entry, so a routine run dirtied the vocagateway submodule
  as a side effect — and vocaphone's git status says nothing about it. It is an
  explicit --favicon PATH flag now.
• ios/VocaPhone.xcodeproj is regenerated for the new files and is in the same
  commit, so the staleness gate is satisfied.
• The keyboard's return key is still .systemBlue (KeyLayout.swift). The key
  palette is a deliberate reconstruction of the system keyboard, greys and all, and
  the blue return key is part of that. Brand-greening it is defensible but it is a
  design decision about the most-used surface in the app rather than a bug.

iOS: 93 tests. Android: 119 tests. just ci exits 0 for iOS, Android and the brand
check. Android's layout changes are compile- and contrast-verified only — no
emulator image or device was available — so they want a look on a real phone.