* fix(test): filter benign Kirigami warning and fix secret prompt lifecycle test

- Filter known benign 'kf.kirigami.platform' QWARN in test_provider_cost_presentation.py
- Fix test_secret_prompt_lifecycle.py to skip zombie check for cli- modes where child intentionally stays alive
- Add langdock provider support (icon, brand color, dashboard URL, docs)
- Update registry size from 90 to 91 providers in README.md and docs/usage.md

* test(secret-prompt): keep the hung-CLI cleanup check for cli modes

The cli-term and cli-kill modes exist to prove that a hung CLI is
killed by the bounded timeout and leaves no running child. Skipping
the process-state check for those modes removed the only assertion
that covers that guarantee. The check passes on main locally and in CI,
so restore it instead of excluding the modes.

* fix(providers): bundle Langdock metadata from official 0.73.0

Langdock joined the registry in official CodexBar 0.73.0, not 0.72.0,
so the README and usage guide now name the 0.73.0 registry. Use the
upstream descriptor's dashboard
(https://app.langdock.com/settings/account/usage) and brand color
(#5A4AE7) instead of placeholder values, and replace the filled
placeholder square with an original currentColor stroke glyph that
matches the other bundled icons and stays legible on dark themes.

Add the translatable fallback name, metadata, name, and API-key
allowlist tests matching the 0.72.0 additions, record the change in the
changelog, and drop the completed TODO item.

---------

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>