#12248: fix: wire streaming config field through resolveExtraParams to streamFn

## Summary - Wire the `agents.defaults.models[key].streaming` config field through `resolveExtraParams()` so it reaches the stream function options - Previously this field was declared in the Zod schema and TypeScript types but never consumed at runtime — `resolveExtraParams()` only read `modelConfig.params`, ignoring the top-level `streaming` boolean - Now `resolveExtraParams()` merges `modelConfig.streaming` into the returned params object, and `createStreamFnWithExtraParams()` passes the `streaming` field through to the streamFn options - This matches the existing Ollama workaround pattern (`params.streaming: false` in model discovery) Fixes #12218 ## Test plan All 3 new tests fail before the fix, pass after: - [x] `resolveExtraParams` includes `streaming` field when set in config (without `params`) - [x] `resolveExtraParams` merges `streaming` with `params` when both are set - [x] `applyExtraParamsToAgent` passes `streaming: false` through to streamFn options (end-to-end) - [x] Existing 4 tests continue to pass - [x] `pnpm build` passes - [x] `pnpm check` passes (lint + format) ## Note on downstream provider consumption The `streaming` field now flows correctly through the OpenClaw config resolution pipeline. However, whether a given pi-ai provider actually reads `options.streaming` to toggle HTTP-level streaming (`stream: true/false`) depends on the pi-ai library. Currently, providers like `openai-completions` hardcode `stream: true` in their `buildParams()` function. This is the same limitation that affects the existing Ollama workaround (`params.streaming: false`). When pi-ai adds per-request streaming control, this config path will "just work." <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR fixes a gap in the embedded runner’s config plumbing: the `agents.defaults.models["<provider>/<modelId>"].streaming` boolean was present in the config schema/types but wasn’t used at runtime. Changes: - `src/agents/pi-embedded-runner/extra-params.ts` now includes `modelConfig.streaming` in `resolveExtraParams()` output, and `createStreamFnWithExtraParams()` passes a boolean `streaming` value through into the streamFn option object. - `src/agents/pi-embedded-runner-extraparams.test.ts` adds focused tests covering (a) `streaming`-only model config, (b) merge with `params`, and (c) end-to-end propagation into streamFn options. This fits into the existing embedded runner pipeline in `src/agents/pi-embedded-runner/run/attempt.ts`, where `applyExtraParamsToAgent()` wraps the session’s `streamFn` to inject provider/model-specific stream options derived from the OpenClaw config. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The change is small and well-scoped: it extends existing extra-param resolution/wrapping to include a boolean `streaming` field, and adds tests to lock the behavior in. I didn’t find any breaking behavior changes beyond the intended config-to-options propagation. - No files require special attention <!-- greptile_other_comments_section --> <!-- /greptile_comment -->