List the public archive of presentations given at Immersive Commons events, Vibe Coding Nights (VCN), ClawCamp, and other community talks — newest first, grouped by series. No auth required. NOT to be confused with ic_resources_list (that lists bookable rooms). Use ic_presentations_get for one VCN session's detail. Args: { series?: string (e.g. 'VCN'|'ClawCamp'|'Talk'), format?: 'deck'|'slides'|'video'|'doc'|'link', limit?: number (max 200, default 100) }. Returns: { count, total, series: string[], scaffold, by_series: Array<{ series, presentations: P[] }>, presentations: P[] (flat) } where P = { session_no (number, VCN-only; null for non-VCN talks), series, title, date, format, public_url, deployed, speaker?, event?, summary? }. `scaffold:true` means placeholder data (real manifest not yet synced). `public_url` is a direct view/download link, null if unpublished (local-only).