Add .gitignore, .editorconfig, REPO_POLICIES.md, and .dockerignore
to bring the repository into compliance with REPO_POLICIES standards.
- .gitignore: Standard template from sneak/prompts plus Go-specific entries
- .editorconfig: root=true, UTF-8, LF, tabs for Go/Makefile, 2 spaces elsewhere
- REPO_POLICIES.md: Copied from sneak/prompts (last_modified: 2026-02-22)
- .dockerignore: Excludes .git, bin/, editor configs, docs; keeps all build files