fix: address PR review on the shielded-pools post

Accuracy, wording, and voice fixes from @oskarth and @rymnc plus two
self-review rounds: retitle to "Exploring Hardened Shielded Pools",
volume wording, light-client target-design caveat, numbered open
problems, FOCIL/Groth16/PIR wording, Kohaku link, the read-side
path-fetch correction with pseudocode, and a voice pass. Schedule the
post for 2026-06-11T07:00:00-04:00 and drop the unused published flag.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Meyanis95