docs: add Memory Defense to the 0.8.2 blog post

[nicoloboschi]

Follow-up to #2172. The 0.8.2 blog post missed Memory Defense, the headline new OSS feature in this release, plus a few smaller items.

Added

• Memory Defense section (lead): per-bank secret/PII scrubbing with the 44-pattern set, redact/block actions, opt-in policy example, and the memory_defense.triggered webhook with new SIEM enrichment fields. Verified new in 0.8.2 (no docs/config at v0.8.1; landed via refactor(memory-defense): per-bank regex defense, webhooks, drop dead surface #2077, feat(observations): enumerate + filter + visualize observation scopes #2149 webhook fields via #f304ce7e0).
• Operational fixes: rolling-deployment migration skip (fix(migrations): catch CommandError-wrapped ResolutionError in rolling-deployment skip #2117), webhook payload missing fields, CLI get-memory parse (fix(cli): parse get-memory response correctly #2111).
• And More: constellation SVG poster export (feat(ui): export constellation as a shareable SVG poster #2099).

Notes

• Did not list integrations in the blog, per the release-blog convention (they keep their own changelogs).
• Docs link uses /developer/memory-defense (docs routeBasePath is /).
• Prettier-clean.