fix: resolve namespace from active profile config

[phil-accelbyte]

Summary

Service commands declaring --namespace as a required parameter were rejected by Clap even when the active profile had a namespace set:

❯ ags profile show
› Profile: default (active)
    Namespace   bjorn
    …

❯ ags ams images list
✕ The following required arguments were not provided:
  --namespace <namespace>

The early resolve_namespace used for Clap arg injection only checked the --namespace flag and AGS_NAMESPACE env var, so the profile-config fallback in ExecutionContext::resolve never got a chance to run — Clap failed first.

This change extends resolve_namespace to also load the active profile's config, matching the resolution order already used by ExecutionContext::resolve: --namespace → AGS_NAMESPACE → active profile config.

Test plan

• Five unit tests in runtime::execution::tests cover the new fallback and the precedence guarantees (flag wins, env wins, explicit --profile, none-when-nothing-set)
• Manual repro: profile with namespace = bjorn, no flag/env → ags ams images list --dry-run now resolves to /namespaces/bjorn/images
• Manual override checks: --namespace flag-ns and AGS_NAMESPACE=env-ns still override the profile value
• cargo clippy --all-targets -- -D warnings clean