[Bug] API Silently Ignores "Reasoning Mode" Disable Flags (Qwen3)

### Describe the issue

The Qwen3 model natively supports disabling its internal block generation via API parameters like "reasoning": false or "chat_template_kwargs": {"enable_thinking": false}. While these parameters work on Ollama and Azure deployments, Foundry Local's /v1/chat/completions API completely strips or ignores them. Passing reasoning disable flags, tuning sampler parameters (e.g., Temperature 0.7, Presence Penalty 1.5), or injecting prompt workarounds (/no_think or empty blocks) all fail. The API passes the request to the runtime in its default state, causing the model to generate massive (2,000+ token) blocks that severely delay response times (up to 4.5 minutes for simple queries).

_(Impact: Developers cannot programmatically disable reasoning mode for fast agentic execution on Foundry Local.)_

### To reproduce

**1.** Load a Qwen3 chat model (we tested qwen3.5-4b) on Foundry Local.

**2.** Send a /v1/chat/completions request with either "reasoning": false or "chat_template_kwargs": {"enable_thinking": false} set.

**3.** Compare against the same model/parameters on Ollama or Azure; reasoning is suppressed there.

**4.** On Foundry Local, observe the model still emitting a large ... block (2,000+ tokens observed) regardless of the flag.

**5.** Additional things we tried that also failed: tuning sampler parameters (Temperature 0.7, Presence Penalty 1.5) to discourage long reasoning, and prompt-level workarounds (/no_think suffix, injecting an empty block into the prompt). None suppressed the behavior.

_(Impact measured: simple queries that should return in a few seconds instead took up to 4.5 minutes due to the unsuppressable reasoning pass.)_

### Urgency

Medium, not a crash, but blocks fast agentic use cases; I had to add a 20s hard timeout wrapper as a workaround.

### Platform and architecture

Windows X64

### OS Version

Windows 11

### Installation type

Released package/binary

### Foundry Local version

0.10.2

### API or surface area

REST API

### Hardware acceleration/backend

CPU

### Backend/runtime version

_No response_

Start by reproducing the request against the /v1/chat/completions REST endpoint with the two Qwen3 disable-flag forms described in the issue. Trace how those parameters are handled before reaching the runtime, then verify that reasoning is suppressed and that the sampler and prompt-workaround cases remain understood. Done means the flags affect the released-package behavior without causing the observed long blocks.

Written by the indexing model from the issue text.