feat: Add Currency Conversion Widget

[haosenwang1018]

This PR adds a new currency conversion widget to Perplexica.

Features

• Real-time exchange rates from exchangerate-api.com (free tier)
• Support for 20+ currencies: USD, EUR, GBP, JPY, CAD, AUD, CHF, CNY, etc.
• Natural language query support (e.g., "Convert 100 USD to EUR")
• Currency name normalization (e.g., "dollars" → "USD")
• Related rates shown for popular currencies as context

Example Queries

• "Convert 100 USD to EUR"
• "What's the exchange rate from JPY to GBP?"
• "How much is 50 euros in dollars?"

Changes

• New currencyWidget.ts following existing widget patterns
• Updated classifier to detect currency conversion queries
• Integrated with search pipeline

Testing

• Follows existing widget architecture (Weather, Stock, Calculator)
• Includes proper TypeScript types
• Error handling for API failures

Fixes #XXX (if there's a related issue)

---

Summary by cubic

Adds a currency conversion widget that answers FX queries with real-time rates. Also adds DeepSeek as a new model provider for chat and embeddings.

• New Features
  • Currency conversion widget: real-time rates from exchangerate-api.com, supports 20+ currencies, natural language queries with name/symbol normalization, and related popular rates. Integrated via showCurrencyWidget in the classifier and registered in the widget executor.
  • DeepSeek provider: chat (streaming, tool calls, object generation) and embeddings. Includes default models (deepseek-chat, deepseek-reasoner, deepseek-embedding) with provider config and registration.

^{Written for commit 67239a3. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 9 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/lib/models/providers/deepseek/deepseekLLM.ts">

<violation number="1" location="src/lib/models/providers/deepseek/deepseekLLM.ts:106">
P2: Inconsistent JSON parsing between streaming and non-streaming paths - `JSON.parse(tc.function.arguments)` can throw on malformed model output. The streaming path uses tolerant `parse` from `partial-json`, and `generateObject` uses `repairJson`, but `generateText` uses raw `JSON.parse` with no fallback. This creates a reliability regression where non-streaming calls can crash on valid but slightly malformed model responses.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: Inconsistent JSON parsing between streaming and non-streaming paths - JSON.parse(tc.function.arguments) can throw on malformed model output. The streaming path uses tolerant parse from partial-json, and generateObject uses repairJson, but generateText uses raw JSON.parse with no fallback. This creates a reliability regression where non-streaming calls can crash on valid but slightly malformed model responses.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At src/lib/models/providers/deepseek/deepseekLLM.ts, line 106:

<comment>Inconsistent JSON parsing between streaming and non-streaming paths - `JSON.parse(tc.function.arguments)` can throw on malformed model output. The streaming path uses tolerant `parse` from `partial-json`, and `generateObject` uses `repairJson`, but `generateText` uses raw `JSON.parse` with no fallback. This creates a reliability regression where non-streaming calls can crash on valid but slightly malformed model responses.</comment>

<file context>
@@ -0,0 +1,228 @@
+                return {
+                  name: tc.function.name,
+                  id: tc.id,
+                  arguments: JSON.parse(tc.function.arguments),
+                };
+              }
</file context>

[xkonjin]

Quick review pass:

• Main risk area here is input validation, path handling, and malformed payload behavior.
• I didn’t see targeted regression coverage in the diff; please add or point CI at a focused test for the changed path in classifier.ts, types.ts, currencyWidget.ts (+6 more).
• Before merge, I’d smoke-test the behavior touched by classifier.ts, types.ts, currencyWidget.ts (+6 more) with malformed input / retry / rollback cases, since that’s where this class of change usually breaks.