feat: switch macro wait steps to templatable seconds

[markwylde]

This change updates macro wait steps to use user-facing seconds values with template support, while preserving backward compatibility with existing durationMs data.

• durationSeconds is now the canonical field for wait_time and wait_inactivity steps.
• Added duration placeholder extraction/rendering for single-brace parameters like {Delay}.
• Runtime now converts rendered seconds to milliseconds at execution time.
• Defaults, normalization, docs, and derived legacy template output were updated accordingly.
• Added E2E coverage for parameterized wait steps and docs for the new behavior.