api: stop applying repeat_penalty 1.1 to models that don't set one

Request options are the model's published parameters and the request's
own options layered over the server defaults, so the default
repeat_penalty of 1.1 reaches every model whose parameters leave it
unset. No maker of the library's current models recommends 1.1: their
generation configs either omit the penalty, meaning 1.0, or pin 1.05.
llama.cpp dropped the same 1.1 default in 2024; vLLM, SGLang, and
transformers apply no penalty. An always-on penalty also distorts
output that legitimately repeats tokens, such as code, JSON, and long
reasoning traces.

The penalty is especially costly for speculative decoding, where
drafts are proposed without it: the penalized target rejects drafted
tokens and the depth controller backs off. On muse-glimmer 30B (DFlash
on M5 Max, HumanEval) the 1.1 default costs 13-16% of end-to-end
throughput at greedy and temperature 1 alike, and drops prose
acceptance at temperature 0.8 from 0.44 to 0.30. On qwen3.6-35B it
cuts the mean accepted draft length from 4.3 to 3.5 tokens and makes
the controller stop speculating on prose.

Defaulting to 1.0 disables the penalty unless a model's parameters or
the request set one. Across the library:

- qwen3, qwen3.6, and qwen3-coder pin their own values (1.0, 1.0, and
  Qwen's recommended 1.05) and are unchanged.
- Everything else local now matches its maker's no-penalty
  recommendation, including gemma2 through gemma4, muse-glimmer, both
  laguna 2.1 models, qwen3.5 (previously 1.1 stacked on its
  presence_penalty of 1.5), gpt-oss, deepseek-r1 and v3.1, the
  nemotron family, granite4, the mistral and llama3/llama4 families,
  phi4, glm4, llava, and devstral.
- qwen2.5 recommends 1.05 but ships no parameters, so it moves from
  1.1 to 1.0 and still needs a parameters layer to conform.
- Cloud models (kimi-k3, deepseek-v4-flash) never receive these
  defaults.

Small older models may repeat themselves more without the penalty
masking it; the remedy is a per-model parameter, not a penalty applied
to every model.