Opening the dedicated /vk/ entry directly in an ordinary browser (no signed VK
launch) fell through to the web flow and silently started a throwaway guest,
which is wrong for a VK-only entry. Mirror the existing /telegram/ launch-error
behaviour: render a compact, shareable, privacy-safe diagnostic screen instead.
- Boot: a new branch `onVKPath() && !insideVK()` sets app.launchError and stops
the fall-through, the VK counterpart of the /telegram/ diagnostic guard.
- Diagnostic (passive, no VK Bridge round-trip): reads the URL launch-parameter
NAMES (never the `sign` value — auth material), whether the URL was signed,
`vk_platform`, the iframe/referrer context, plus the shared client-environment
lines. VK signs the launch URL at load, so — unlike Telegram's initData — the
parameters never arrive late; hence the VK screen offers Share only, no Retry.
- Generalise the screen: TelegramLaunchError.svelte -> LaunchError.svelte, which
renders a neutral pre-formatted report and a per-platform title, with Retry
gated on a `retry` flag (Telegram true, VK false). app.launchError is now a
neutral LaunchDiag { platform, report, retry }.
- New lib/launchdiag.ts holds the shared pieces both platforms reuse: the
LaunchDiag shape, the client-environment lines, and the query field-NAME
reader (moved out of telegram.ts so VK does not duplicate them).
Tests: pure vkDiagLines units, incl. a guard that the `sign` value never leaks
into the report. i18n: launch.errorTitleVk (en/ru). Docs: FUNCTIONAL (+ru) user
story and ARCHITECTURE entry-path note.
Ilia Denisov