feat(cli): add generic output formatter to eliminate --output flag duplication (#1753)

* feat(cli): add generic output formatter to eliminate --output flag duplication

Closes #1750

Creates a new output.rs module with generic helper functions for formatting
CLI command output in JSON, YAML, or table formats. This eliminates ~38 lines
of duplicated code across 4 commands, provides a single source of truth for
output formatting, and makes it easier to add new output formats in the future.

Changes:
- crates/openshell-cli/src/output.rs: New module with 6 helper functions and 14 tests
- crates/openshell-cli/src/lib.rs: Register output module
- crates/openshell-cli/src/run.rs: Migrate 4 commands to use helpers
  - gateway_list(): 23 lines → 5 lines
  - sandbox_list(): 17 lines → 5 lines
  - provider_list_profiles(): 12 lines → 7 lines
  - provider_profile_export(): 11 lines → 8 lines
- architecture/cli.md: New CLI architecture documentation
- architecture/README.md: Add reference to CLI architecture doc

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Jeff MAURY <jmaury@redhat.com>

* fix: apply recommandations from gator-agent

Signed-off-by: Jeff MAURY <jmaury@redhat.com>

* fix: fix wrong CLI output test

Signed-off-by: Jeff MAURY <jmaury@redhat.com>

---------

Signed-off-by: Jeff MAURY <jmaury@redhat.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: jeffmaury

crates/openshell-cli/src/lib.rs

@@ -12,6 +12,7 @@ pub mod auth;
 pub mod completers;
 pub mod edge_tunnel;
 pub mod oidc_auth;
+pub mod output;
 pub(crate) mod policy_update;
 pub mod run;
 pub mod ssh;