fix(server): reject malformed UTF-8 Connector responses

[xuedingjie]

Problem

ConnectorClient decoded upstream response bytes with Buffer.toString('utf8'). Malformed UTF-8 was replaced with U+FFFD before JSON parsing, so a response such as a Team/Provider name could be accepted with data different from the bytes returned by the Connector service.

Fix

Decode Connector JSON responses with a fatal UTF-8 decoder. The existing connector.unavailable error mapping remains unchanged. Add a regression test using an invalid UTF-8 sequence in a Teams response.

This matches the strict decoding used by Integration callbacks and follows the JSON UTF-8 requirement in RFC 8259 section 8.1.

Verification

• npx --yes bun@1.4.0 x vitest run --config vitest.config.ts test/connectorClient.test.ts -t "malformed UTF-8"
• npx --yes bun@1.4.0 x oxfmt --check apps/server/node/connector.ts apps/server/test/connectorClient.test.ts
• npx --yes bun@1.4.0 x oxlint --deny-warnings apps/server/node/connector.ts apps/server/test/connectorClient.test.ts
• npx --yes bun@1.4.0 x tsc --noEmit -p apps/server/tsconfig.json

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 59bec4a and a477ef0.

📒 Files selected for processing (2)

• apps/server/node/connector.ts
• apps/server/test/connectorClient.test.ts

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