feat(web): redesign the Providers settings panel

Show each provider's config form first, collapse the model table into a
toggle with a count, and put a red delete icon next to every provider row
instead of a button at the bottom of the page.

Also fix two causes of the form showing stale or empty data: the edit form
is now keyed by provider id so switching providers re-seeds it, and it
re-reads the config when that request resolves after mount. Model rows fall
back to the catalog (with real context sizes) when the config section has
no entries for the provider.

Author: elkaix

.changeset/providers-panel-redesign.md

@@ -0,0 +1,5 @@
+---
+"@pymodel/pythinker-code": minor
+---
+
+Redesign the Providers settings: each provider shows its own config first with models in a collapsible section, and a delete icon sits next to every provider.

apps/pythinker-code/dist-web/.web-bundle-manifest.json

@@ -1,4 +1,4 @@
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 }