docs: changelog and blog post for v0.8.4

[nicoloboschi]

Changelog and blog post for v0.8.4 (precedent: #2053, #2080, #2290).

Note

Docs-only PR. The v0.8.4 tag has not been cut yet — the changelog was generated against origin/main (4c307ce4e). Re-generate against the real tag once release.sh 0.8.4 runs if the range shifts.

Files

• hindsight-docs/src/pages/changelog/index.md — generated 0.8.4 entry (13 features / 11 improvements / 24 bug fixes), covering everything since v0.8.3 (2026-06-18).
• hindsight-docs/blog/2026-06-30-version-0-8-4.md — hand-written release blog (passes prettier --check).
• skills/hindsight-docs/references/changelog/index.md — synced skill mirror (generate-docs-skill.sh).

Blog highlights

• Multi-LLM failover & round-robin routing — survive provider outages; per-member LiteLLM Router / Vertex SA key / project-region config; new Requesty & Atlas Cloud providers.
• Finer recall control — per-stage scores, two-level min_scores, configurable recency decay, prefer_observations dedup.
• Scheduled mental-model refresh (cron).
• Sharper LLM control & accounting — per-operation temperature, per-scope timeouts/retries, cached/thoughts/reasoning token accounting.
• Data-integrity & robustness fixes — with an upgrade recommendation for self-managed deployments.

Integrations are intentionally kept out of the blog (each ships its own changelog); they still appear in changelog/index.md, matching precedent.