Add comprehensive file-level DOX documentation across the repo and update directory AGENTS.md indexes. Many new `*.py.dox.md` files were added under api, helpers, tools, plugins, extensions, webui, and other dirs to document endpoint purpose, ownership, runtime contracts, work guidance, and verification. Several AGENTS.md files were created or updated (agents profiles, api, docker, extensions, helpers, plugins, skills, webui components, etc.) to list child DOX files and clarify documentation/work guidance. Also add example and bundled profile DOX files (agent0, default, developer, hacker, researcher) and minor updates to helpers/dirty_json.py and its tests. These changes improve on-disk documentation coverage and establish the convention that each direct runtime file should have a matching `*.dox.md` describing its contracts and verification steps.
- Fixes SearXNG startup failure in the Docker container caused by `wikidata` engine init raising `KeyError: 'name'`.
- Adds a default-settings engine override to remove `wikidata` during initialization in both base and run image SearXNG configs.
- Change X-OpenRouter-Categories from YAML list to comma-separated string
- Add pipx to base Python installation
- Truncate long lines in code execution output to 500 chars (250 from each end) before prompt detection
- Reorder model config UI sections and simplify plugin config button handler
- Remove border/padding from model summary grid and adjust mobile responsive styles
