Document deterministic per-worktree port and URL patterns

[adrianmross]

Problem

Side-by-side worktrees are much easier to use when each branch gets a deterministic local port and discoverable URL, but the plugin does not currently surface that WorkTrunk pattern.

Proposal

• Add reference docs for {{ branch | hash_port }} usage
• Show how to expose URLs via wt list metadata
• Include cleanup guidance in pre-remove
• Provide examples suitable for local web services and API servers

Why

This improves the day-to-day experience of running multiple branches in parallel without adding tmux automation or extra wrappers.