fix: ChatBubble crash and DeepSeek API compatibility

- Fix ChatBubble to handle non-string content with String() wrapper
- Fix API route to use generateText for non-streaming requests
- Add @ai-sdk/openai-compatible for non-OpenAI providers (DeepSeek, etc.)
- Use Chat Completions API instead of Responses API for compatible providers
- Update ChatBubble tests and fix component exports to kebab-case
- Remove stale PascalCase ChatBubble.tsx file

_bmad-output/settings-page-snapshot.txt

@@ -0,0 +1,21 @@
+uid=1_0 RootWebArea "Test01 - Local-First Venting" url="http://localhost:3000/settings"
+  uid=1_1 heading "Settings" level="1"
+  uid=1_2 StaticText "Manage your AI provider and preferences."
+  uid=1_3 heading "Active Provider" level="2"
+  uid=1_4 StaticText "Select which provider to use for new chats."
+  uid=1_5 radio "Default Provider (Migrated) gpt-4o Active" checked
+  uid=1_6 StaticText "Default Provider (Migrated)"
+  uid=1_7 StaticText "gpt-4o"
+  uid=1_8 StaticText "Active"
+  uid=1_9 heading "Manage Providers" level="2"
+  uid=1_10 StaticText "Add, edit, or remove your AI providers."
+  uid=1_11 button "Add Provider" expandable haspopup="dialog"
+  uid=1_12 heading "Default Provider (Migrated)" level="3"
+  uid=1_13 StaticText "Model: "
+  uid=1_14 StaticText "gpt-4o"
+  uid=1_15 StaticText "https://api.openai.com/v1"
+  uid=1_16 button "Edit provider"
+  uid=1_17 button "Delete provider"
+  uid=1_18 button "Add New Provider"
+  uid=1_19 StaticText "Offline - Saved locally"
+  uid=1_20 button "Open Next.js Dev Tools" expandable haspopup="menu"