feat: conversation log + system prompt overrides (#9)

fix: address CodeRabbit review findings

docs: add AGENTS.md convention across all directories

feat: thinking transparency layer with /verbose command

refactor: remove specialists, schemas, dummy agent; extract model config

feat: add native agent tools, /tools command, and fix rendering bugs

feat: generalize agent orchestration and externalize prompts to YAML

functional testing

initial commit: modular textual tui with async agent loop