Expose the merged runtime settings through a direct CLI subcommand so
users can inspect the effective configuration without entering the REPL.
The command prints the merged config as pretty JSON and is covered by
unit and end-to-end tests.
Constraint: Must preserve existing config precedence and read the same merged runtime config used by the CLI
Rejected: Reuse the text `/config` report output | user requested machine-readable JSON
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Keep `claw config show` aligned with `ConfigLoader` precedence rules if config discovery changes
Tested: `cd rust && cargo build --workspace`; `cd rust && cargo test --workspace`
Not-tested: Manual invocation against a real user config outside test fixtures
Yeachan-Heo