Frostbite minimal

Everything is authored at the *exact* native pixel geometry of the vanilla 26.3
client, so the pack scales cleanly at every GUI scale setting with zero layout
drift. No `.mcmeta` sidecars are needed: all nine-slice scaling and animation
rules fall back to the vanilla defaults, and the artwork is drawn to match them.

## What it changes

| Area | Result |
| --- | --- |
| Container screens | Frosted-glass panels with recessed slot wells and brushed-metal borders, covering the survival inventory, chests (`generic_54`), crafting table, furnace / smoker / blast furnace, enchanting table, anvil, smithing, brewing stand, hopper, dispenser, shulker box, loom, cartography table, stonecutter, crafter, beacon, horse, villager, the creative item tabs and the container progress sprites (flames, arrows, bubbles, experience bars, error marks, scrollers) |
| HUD | Health, hunger, armour, air, XP and jump bars as sleek icy-blue gradients, with a redesigned translucent hotbar, selection frame and off-hand slots |
| Crosshair | Minimalist reticle with a clear centre and faded tips, plus a matching attack-cooldown ring and hotbar bar |
| Menus & widgets | Icy-slate buttons, sliders, text fields, checkboxes, tabs, scrollbars, tooltips, popups, ping bars, server/world-list icons, the recipe book, social-interaction controls and the friends list, plus the menu backgrounds and separators |
| Typography | A re-authored pure-white bitmap font that reproduces vanilla's letterforms pixel for pixel, so text looks like ordinary Minecraft text |
| Pack icon | `pack.png`, a frosted plate with an icy reticle |

The only vanilla GUI textures the pack deliberately leaves alone are Mojang
branding artwork: the title logos and panorama, the Realms promo art and the
superflat preset thumbnails. Everything else in the vanilla GUI -- including
the advancement tab tiles and the Realms status badges -- is redrawn here.