feat: flatten opportunity commands, add config management, fix completions

- Flatten opportunity into top-level portfolio and opportunity commands
- Add interactive config get/set/key/secret with type coercion
- Rewrite --doc to show TUI vs JSON schema per command
- Unify agent mode output to JSON only
- Make init prompt for API key/secret interactively
- Fix coin tab completion alias binding
- Fix set_config_value reading from wrong path
- Fail loudly on invalid numeric config values

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pyproject.toml

@@ -13,6 +13,7 @@ dependencies = [
   "binance-connector>=3.9.0",
   "shtab>=1.7.0",
   "tomli>=2.0.1; python_version < '3.11'",
+  "tomli-w>=1.0.0",
 ]
 
 [project.optional-dependencies]