[SaladDay]

Change

Preserve system for thinking-enabled custom OpenAI Chat Completions connections to api.siliconflow.cn and api.siliconflow.com.

Only the default message-role capability changes for these exact hosts. Thinking, explicit compatibility overrides, other request options, and other endpoints retain their behavior. Kimi (#206) and DashScope (#207) are inherited unchanged. Authentication, thinking-toggle behavior, and connection-test redesign are outside scope. This PR targets main after #207 was squash-merged.

Stack

main -> #209 -> #210

#207 is already merged. Merge #209 first. After #209 is squash-merged, synchronize #210 with the new main and retarget it to main before merging. Changing the base alone does not reconcile squash-merged ancestry. Each PR is reviewed against its immediate base.

Evidence

• SiliconFlow's official Chat Completions schema does not include developer in the accepted message roles.
• OpenClaw's compatibility detection disables developer role by default for configured non-OpenAI endpoints.
• OpenCode's compatible chat protocol uses a serializer that preserves system messages.
• pi's SiliconFlow provider proposal also sets supportsDeveloperRole: false for api.siliconflow.com. It was closed without merging; the proposal is supporting context, not an upstream release claim.

Validation

• Focused resolver suite: 97 tests passed, covering both official hosts, unrelated host/path matches, preserved reasoning, and explicit compatibility overrides. The newly covered endpoint failed before the matcher update.
• Full verification: all 14 gates passed on macOS arm64 / Node 26.7.0 at 23aacf0.
• Fresh independent blind review of the stacked changes found no actionable issues; git diff --check passed.

Publication and maintainer handoff

• Existing licenses and notices are preserved; publication scope is unchanged.
• No credentials, account data, user content, private review material, or internal history is included.
• No source files were added or removed; tests extend an already registered file.
• Documentation impact is limited to the vendored patch ledger.
• Shared-source port: pending.

The merge-base changed after approval.