DingTalk bot unbind was routed through the generic adapter config update,
but undefined credential fields are dropped during JSON serialization. That
left stored Client ID and Secret values intact after clicking the unbind
button. Match the working WeChat path with a dedicated server endpoint and
frontend API call so credential removal is explicit.
Constraint: JSON request bodies cannot preserve undefined fields for generic config clearing
Rejected: Keep using updateConfig with undefined fields | serialized requests omit the fields before the server can clear them
Confidence: high
Scope-risk: narrow
Directive: Keep credential-clearing flows on explicit unbind endpoints rather than relying on partial config merges
Tested: bun test src/server/__tests__/adapters.test.ts
Tested: cd desktop && bun run test src/stores/adapterStore.test.ts
Tested: bun run check:desktop
Tested: bun run check:server
Not-tested: bun run quality:pr is blocked by repository policy requiring allow-cli-core-change approval for the broader branch impact
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