Agent Skills: ticket-write

I-phase skill for the ticket-writing workflow. Drafts the ticket section-by-section per the Writing Plan from ticket-plan. Pre-dispatches all planned subagents in parallel before writing begins (efficiency win); iterates through sections in writing order; pauses at planned checkpoints for user review. Each section follows AGENT-BRIEF discipline: durability over precision (no file paths, no line numbers); behavioral, not procedural; complete acceptance criteria; explicit scope boundaries. Hands off to ticket-verify.