refactor(cli): change --ideas-list flag to idea list subcommand

- Removed --ideas-list flag from top-level options
- Added 'idea list' subcommand under idea command
- Removed ideasList from CliOptions interface
- Updated help text to show idea list subcommand
- Updated CHANGELOG.md to reflect new command structure
- Updated cli.test.ts to test idea command availability

This makes the CLI structure more intuitive:
  opencoder idea 'description'  - Add an idea
  opencoder idea list              - List all ideas

Signed-off-by: leocavalcante <[email protected]>

Author: leocavalcante

src/cli.ts

@@ -316,7 +316,6 @@ export function parseCli(argv: string[] = process.argv): ParsedCli {
 			commitSignoff: opts.signoff as boolean | undefined,
 			status: opts.status as boolean | undefined,
 			metricsReset: opts.metricsReset as boolean | undefined,
-			ideasList: opts.ideasList as boolean | undefined,
 		},
 		hint: args[0],
 	}