Add visible progress and interactive Grok handoff

[Walvez]

What changed

• add revision-based visible Grok progress with plan, tool activity, elapsed time, public response previews, and user-facing heartbeats
• add a macOS interactive handoff mode that opens the official Grok TUI in a separate Terminal window
• isolate interactive implementation work in a Grok-created Git worktree
• document lifecycle, security boundaries, and bilingual usage
• bump the plugin to version 0.3.0

Why

Managed Grok sessions previously collected status without reliably surfacing it to the user. Some long-running tasks are also better handed directly to an interactive Grok window instead of being continuously supervised by Codex.

Safety

• private thought chunks remain discarded
• initial interactive prompts use mode-0600 temporary files and are removed before Grok starts
• interactive write handoffs cannot target the primary checkout
• commit, push, merge, and publication are not authorized by the handoff

Validation

• npm test
• 9/9 Node tests passed
• MCP smoke test passed with 9 tools
• marketplace and plugin layout validation passed