restructure docs: split triggers into usage pages, add model resolution docs

- split triggers.mdx into direct-prompting, pr-reviews, issue-enrichment, coding-tasks
- rename manual-setup.mdx to headless-action.mdx (CI integration)
- reorganize sidebar into Getting started / Usage / Reference groups
- add redirects for /triggers and /manual-setup
- add PULLFROG_MODEL env var support across action, workflows, and docs
- rewrite models.mdx with aliases, free models, resolution chain, routers
- update all cross-references in app, components, and docs

Made-with: Cursor

.github/workflows/test.yml

@@ -41,6 +41,7 @@ jobs:
       OPENROUTER_API_KEY: ${{ secrets.OPENROUTER_API_KEY }}
       MOONSHOT_API_KEY: ${{ secrets.MOONSHOT_API_KEY }}
       OPENCODE_API_KEY: ${{ secrets.OPENCODE_API_KEY }}
+      PULLFROG_MODEL: ${{ vars.PULLFROG_MODEL }}
       OPENCODE_MODEL: ${{ vars.OPENCODE_MODEL }}
     steps:
       - uses: actions/checkout@v6