UX: inconsistent short flags across clean / prune / push

[sauravpanda]

Problem

Short flags and confirmation conventions vary between destructive commands:

• clean — uses -s for --stale
• prune — has both --stale and -s, and uses -y for --yes
• push — uses -r for --remove, no -y counterpart (see bug: push --remove deletes worktree without confirmation #54)

Users can't rely on muscle memory across commands, and -r vs -y conventions drift.

Suggested fix

Audit all destructive/mutating commands and standardize:

• -y / --yes everywhere for skip-confirmation
• -n / --dry-run where applicable
• -f / --force where applicable

Document the convention in the README.