Initial SQL-only 1C adapter baseline

docs/model-selection.md

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+# First Model Selection
+
+## Selected Model
+
+`Qwen/Qwen3-4B-Instruct-2507`
+
+Local served name: `qwen3-4b-instruct`.
+
+## Why This Model
+
+- Apache-2.0 license.
+- 4B parameters, so it is a practical first GPU deployment target.
+- Supports text generation, chat, coding, multilingual tasks and tool-use scenarios.
+- Official model page includes vLLM usage.
+- Native context length is 262,144 tokens, but the first deployment uses 32,768 tokens to reduce OOM risk until GPU VRAM is confirmed.
+
+## Alternatives
+
+- `Qwen/Qwen3-8B`: stronger base candidate, but requires more VRAM.
+- `Qwen/Qwen3.5-4B`: newer and long-context oriented, but its model card currently recommends newer/mainline serving frameworks, so it is better as a second experiment after the first stable deployment.
+- Mistral/DeepSeek coder models: useful future candidates for coding-specific comparison, but not the first default for Russian + 1C + general assistant coverage.
+
+## Sources
+
+- https://huggingface.co/Qwen/Qwen3-4B-Instruct-2507
+- https://huggingface.co/Qwen/Qwen3-8B
+- https://huggingface.co/Qwen/Qwen3.5-4B