feat(platform): promote namespace to GA

[smukherjee-godaddy]

Summary

• remove the Experimental feature flag from the platform command group
• expose platform app, actions, and webhook commands at the default GA stage
• update platform visibility and command-tree tests

Validation

• cargo fmt --check
• cargo check
• cargo test (693 passed)
• ./scripts/check-module-size.sh
• cargo run --quiet -- platform --help

Note: cargo clippy -- -D warnings currently fails on main at rust/src/config/settings_form.rs:275 (clippy::collapsible-match), which is outside this PR.