Fix non-ASCII keyboard input (ä ö ü ß, AltGr €) in Blit graphical apps and terminals

[haraldschilly]

German-layout users cannot type ä ö ü ß or AltGr+€ into Blit. Investigation
found two independent causes, only one of which is ours. Full notes, with
code references for every claim, are in
src/.agents/blit-keyboard-layout-20260826.md.

1. Terminals: projects had no locale (fixed here)

Projects ran with no LANG at all. Confirmed on cocalc.ai:

$ echo "$LANG"; locale
LANG=
LC_CTYPE="POSIX"
...

In the C locale readline enables convert-meta, which mangles every multi-byte
character — the classic "umlauts don't work in a container" problem. Anything
that trusts LC_CTYPE for its input encoding fails the same way, Blit's PTYs
included.

getEnvironment() now defaults LANG to C.UTF-8, which is always present and
needs no locale generation. An image naming its own locale keeps it. The
workspace runtime was never affected — its inherited-env allowlist already
passes the locale variables through from the host, which is also why local dev
never reproduced this.

2. Graphical windows: apps silently running on X11 (partly fixed here)

Blit's compositor compiles in a single US-QWERTY XKB keymap and has no way to
change it. The browser compensates by resolving the user's layout itself and
sending printable characters as text rather than keycodes — that part works, and
e.key is "ä" as it should be. But the compositor synthesises evdev keys only
for the ASCII subset US-QWERTY can express, and routes everything else through
zwp_text_input_v3.commit_string alone. A client that never enables an input
method drops those characters, and X11 clients cannot bind the protocol at all.

So any app that ends up on Xwayland loses all non-ASCII input. Three apps in our
catalog were on the wrong side of that line:

• Krita and TeXstudio — likely the most consequential, because it failed
  silently. Blit exports QT_QPA_PLATFORM="wayland;xcb", and Qt falls back to
  xcb without complaint when its Wayland platform plugin is missing. Nothing
  installed one, so both ran as X11 clients despite the hint. They now pull
  qt6-wayland and qtwayland5 (both generations, since the packaged Qt
  version moves between Ubuntu releases).
• Chromium — launched with --ozone-platform=wayland but not
  --enable-wayland-ime. Chromium binds zwp_text_input_v3 only when its
  Wayland IME support is on, so it never received a commit_string.
• Emacs — installed emacs-gtk, the X11 build. emacs-pgtk is the same
  editor built against GTK for Wayland.

What this does not fix

IDLE, XClock, and GIMP 2.x on Ubuntu 24.04 have no Wayland build to switch
to — Tk has no Wayland backend at all. They stay broken for non-ASCII input
until Blit grows a fallback for clients without text-input.

Reported upstream as indent-com/blit#317, with the
mechanism and a suggested direction (bind a spare keycode to the needed keysym,
push the updated keymap via wl_keyboard.keymap, press, restore — the approach
xdotool/wtype use; Blit already owns the keymap bytes). We are not sending a
PR for it. No prior upstream issue existed — a search for keymap, xkb, layout,
text-input, umlaut, AltGr and plain "keyboard" returned nothing.

Also worth knowing: the launcher skips installation once an app's executable
exists, so a project that already installed Krita or TeXstudio keeps the old
package set and is not repaired by this.

Ruled out

Version skew (we pin Blit 0.55.1, effectively upstream HEAD), iframe embedding,
and a per-account keyboard-layout setting — there is nothing for such a setting
to attach to, since the keymap is compiled into the Blit binary and the browser
already applies the user's real layout.

Validation

Unit tests for both changes; pnpm tsc and lint:frontend clean.

Verified on the local Launchpad dev stack (Multipass project host, podman
runtime):

• The locale bug reproduces locally, matching cocalc.ai exactly — inside a
  running project container, LANG is empty and LC_CTYPE="POSIX".

• Every new package name resolves, on both Ubuntu releases, so the app
  installer cannot break on a bad name (it runs apt-get install -y under
  set -euo pipefail, where one missing package fails the whole install):

  package	24.04	26.04
  emacs-pgtk	1:29.3+1-1ubuntu2	1:30.2+1-2ubuntu1
  qt6-wayland	6.4.2-5build3	6.10.2-4
  qtwayland5	5.15.13-1	5.15.18-1

  Worth noting Krita on 24.04 is 5.2.x (Qt5) while 26.04 has 6.x — which is
  exactly why both Qt generations are listed rather than just one.

Still unverified end-to-end: that LANG actually arrives as C.UTF-8 in a
container. getEnvironment() runs in the project-host inside the VM, so proving
it live needs a project-host bundle rebuild, version pin, and reconcile. The
pre-fix state is confirmed reproduced, and the change is unit-tested.

Also unverified: the umlaut round-trip itself, which needs a browser on a German
layout typing into the Blit iframe.

[blacksmith-sh]

Found 15 test failures on Blacksmith runners:

Failures

Test	View Logs
account/tests/membership-package-manager.test.tsx/ lets admins add site-license delegates with admin user search	View Logs
admin/receivables/create.test.tsx/ previews and fresh-authenticates an explicit order submission	View Logs
admin/receivables/detail.test.tsx/ shows a friendly payment rejection inside the active modal	View Logs
Blit application launcher/runs Chromium's repository installer after confirmation	View Logs
Blit application launcher/runs Chromium's repository installer after confirmation	View Logs
frame-editors/x11-editor/blit-launcher.test.tsx/ runs Chromium's repository installer after confirmation	View Logs
membership package managers/ lets admins add site-license delegates with admin user search	View Logs
membership package managers/ lets admins add site-license delegates with admin user search	View Logs
membership package managers/ lets admins add site-license delegates with admin user search	View Logs
membership package managers/ lets admins add site-license delegates with admin user search	View Logs

...and 5 more test failures. View all on Blacksmith

^{Need help on this PR? Tag @codesmith-bot with what you need.}

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