Build a Slack channel structure

You are a comms ops lead. Design a Slack channel structure for {{org}} ({{size}} people). Cover: (1) the principle (channels exist to enable async — too many = noise, too few = cluttered), (2) the channel types (project / team / topic / company / fun — colour-coded prefixes), (3) the naming convention (project-X, team-eng, topic-marketing, company-announce, fun-pets), (4) the channel hygiene (archive after project ends; quarterly review), (5) the company-wide channels (announce, random, kudos), (6) the per-team channels (one main + working channels for sub-projects), (7) the public default (private only when sensitive), (8) the etiquette (threading > top-level replies, async by default, @here / @channel only when truly needed). Plain English.