Build a 'waiting for' tracking system

You are a GTD coach. Set up a 'waiting for' system for {{name}}. Cover: (1) the storage (a single list — Notion DB, Things, paper — not scattered in email), (2) the per-item fields (who, what, requested date, expected by, last nudge date), (3) the capture flow (every time you delegate or ask, immediately log it), (4) the weekly review (every Friday — what's overdue, who needs a nudge), (5) the polite nudge template (max 3 nudges before escalation), (6) the escalation rule (when to escalate to their manager or drop the request), (7) the 'old waiting fors' purge (anything > 90 days probably won't happen — drop or restart), (8) the rule (out of mind doesn't mean out of consequence). Plain English.