chore: Wave 1 foundation - pin deps, add ignore files, parameterize format.ts, resettable config

- Pin @opencode-ai/plugin to 1.2.27 and bun-types to 1.3.11
- Add .dockerignore and update .gitignore with .env, evidence/, test-results/
- Parameterize formatUnexpectedError with toolName prefix, add createToolErrorFormatter
- Add resetConfigValidation for test isolation

Tasks: 1-4 complete