fix(js/plugins/compat-oai): update model extraction logic to use slice instead of pop for better path handling

[sd0ric4]

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Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually)
• Docs updated (updated docs or a docs bug required)

When I was using OpenRouter as the provider, I discovered this issue: the previous approach using .pop() cannot preserve any of the / separators, which is problematic.

Main Drawback: Cannot Handle Model Names with Multiple '/' Separators

const name = 'openrouter/deepseek/deepseek-chat-v3-0324:free';

// Problem with using .pop():
name.split('/').pop() // Only returns the last part: 'deepseek-chat-v3-0324:free'

// You lose all the important middle information:
// - 'deepseek' (model family)
// - Only 'deepseek-chat-v3-0324:free' remains (specific model)

Former

Now

import {
  compatOaiModelRef,
  defineCompatOpenAIModel,
  openAICompatible,
} from '@genkit-ai/compat-oai';
import { genkit } from 'genkit/beta';

export const deepseekRef = compatOaiModelRef({
  name: 'openrouter/deepseek/deepseek-chat-v3-0324:free',
});

export const ai = genkit({
  plugins: [
    openAICompatible({
      name: 'openrouter',
      apiKey: process.env.OPENROUTER_API_KEY,
      baseURL: 'https://openrouter.ai/api/v1',
      initializer: async (ai, client) => {
        // Register a text model
        defineCompatOpenAIModel({
          ai,
          name: deepseekRef.name,
          client,
          modelRef: deepseekRef,
        });
      },
    }),
  ],
});

const llmResponse = await ai.generate({
  model: deepseekRef,
  prompt: 'Tell me a joke about a llama.',
  config: {
    temperature: 0.9,
  },
});

console.log('llmResponse:', JSON.stringify(llmResponse, null, 2));

console.log('llmResponse (detailed):');
console.dir(llmResponse, { depth: null, colors: true });