docs: migrate README to API-Doc-Convention (S2-cascade.libs)

Restructured per ADR-0038: Abstract + bold-list Badges + Topology H2
+ H3-API-Subsections (one per public function) + Conventions/Consumer
pattern/CHANGELOG/References.

Topology auto-populated via Sporel.exe --lint --fix. Pre-commit hook
installed via --install-hooks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/install-hooks.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+git config core.hooksPath .githooks
+echo "Hooks activated."