Add a scannable content overview below the v13 release-note hero

Context

A 4-human review of resources/content/release-notes/v13.0.0.md flagged it as a 30+ minute read — too long for the primary scan path. The doc already has a fast-reader scan layer (the "Curated Changelog Digest" + its Corpus→Digest→Reader diagram), but it sits at the bottom, after the full narrative, so a time-pressed reader hits the deep story first and never reaches it.

The Fix

Lift a tight, scannable overview to directly below the hero/TL;DR: a one-line gist + a 5-hero-chapter map (Brain / Institution / Identity / Dream / Cloud, one line each) + reader-paths, framing the deep narrative as opt-in depth. Overview-first, no content cuts — preserves the proof corpus for deep auditors + SEO/GEO + agent-ingestion.

Acceptance Criteria

• A concise "v13 in 2 Minutes" overview section is added directly below the TL;DR blockquote (above the first narrative chapter).
• It carries the one-line gist + a per-hero-chapter one-liner + reader-paths.
• No existing narrative or changelog content is removed.

Out of Scope

• Cutting or splitting the narrative chapters — a separate, larger edit only if the overview alone doesn't resolve the "too long" feedback.

Origin Session ID: efc94c7f-3004-42e2-89cd-ed4102d9d2d7