fix(settings): show live models in default model picker and apply to new chats (#872) (#900)

* fix(settings): show live models in default model picker and apply to new chats (#872)

Two related bugs:
1. Settings > Preferences > Default Model dropdown only showed static models
   from /api/models — live-fetched models (e.g. @nous:anthropic/claude-opus-4.7)
   were missing. Now calls _fetchLiveModels() on the settings picker too.
2. New chats ignored the saved default model preference — they always used the
   chat-header dropdown value (which reflects the previous session's model).
   Now newSession() uses the saved default_model and syncs the dropdown.

Extracted _addLiveModelsToSelect() from _fetchLiveModels() so cached live models
can be applied to any <select> element (chat-header or settings picker).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* fix(tests): update live-model prefix tests for _addLiveModelsToSelect extraction

The tests searched for og.dataset.provider, _isPortalFetch, and openrouter
exclusion patterns inside _fetchLiveModels(). These were extracted into
_addLiveModelsToSelect() as part of the #872 fix. Updated regex targets to
check _addLiveModelsToSelect first, falling back to _fetchLiveModels.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* chore: add multi-tab note on window._defaultModel

Clarifies that window._defaultModel is per-page-load and not synced
across browser tabs, following maintainer feedback on #889.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* chore: CHANGELOG for v0.50.170

* chore: trigger PR refresh after rebase

---------

Co-authored-by: fr33m1nd <bergeouss@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>

CHANGELOG.md

@@ -29,6 +29,11 @@
   workspace subtree) and never enumerate blocked system roots. (`api/routes.py`,
   `api/workspace.py`, `static/panels.js`, `static/style.css`) (partial for #616)
 
+## [v0.50.170] — 2026-04-23
+
+### Fixed
+- **Settings default model picker shows live-fetched models** — the Settings → Preferences → Default Model dropdown previously only showed static models from `_PROVIDER_MODELS`. It now calls `_fetchLiveModels()` via the new `_addLiveModelsToSelect()` helper, consistent with the chat-header dropdown. New sessions also respect the saved default model (`window._defaultModel`) instead of always reading the chat-header value, which reflected the previous session's model. (`static/ui.js`, `static/sessions.js`, `static/panels.js`) Closes #872. Co-authored by @bergeouss.
+
 ## [v0.50.163] — 2026-04-23
 
 ### Fixed