docs(connectors): prep 2026.6.1 release notes and group connectors by kind [roadmap:rac-connectors]

[tcballard]

Pre-release docs polish for rac-connectors 2026.6.1. Two commits:

1. CHANGELOG for 2026.6.1

• Adds CHANGELOG.md with the 2026.6.1 entry (release-notes home) — first published release, renamed from lore-connectors, the connector set, and the lore_id → rac_id outbound field change (ADR-095).

2. Group connector pages by kind

• Each connector page gains a category: field; the generated ## Connectors section is now grouped under kind headings instead of a flat list:
  • Memory & RAG — Supermemory, Mem0, Letta
  • Knowledge graph — Zep, Cognee, Neo4j
• Grouping is by kind, not direction, so a provider that does both ingest and export (e.g. a future Atlassian suite) sits in one kind group, with its direction described on its own page.
• Kind headings are data-driven in scripts/sync_readme.py (ordered by the lowest order in each kind), so a new page slots its kind into place via order alone. Regenerated and --check-clean.

Release-readiness (verified on merged main + this branch)

• 125 tests pass; build is clean and the version derives from the tag → rac_connectors-2026.6.1 (wheel + sdist).
• Publish workflow targets rac-connectors (OIDC to pypi.org/p/rac-connectors), fires on Release published, gated on full CI.

How to cut the release (your action)

1. Merge this PR (merge commit).
2. Tag 2026.6.1 on main (repo convention is non-padded month YYYY.M.N, ADR-008).
3. Publish a GitHub Release for that tag (CHANGELOG entry as the body) → the workflow builds and publishes to PyPI. This also reserves the rac-connectors name on PyPI.

Execution tracking: asdecided/core#228 (rac-connectors).