chore(release): bump to 3.3.0 and curate CHANGELOG

[igorls]

Summary

Prepare develop for the 3.3.0 release cycle — version strings bumped everywhere and CHANGELOG cleaned up to professional standard.

Version bumps

• mempalace/version.py: 3.2.0 → 3.3.0
• pyproject.toml: 3.2.0 → 3.3.0
• README.md:717 pyproject.toml label: v3.2.0 → v3.3.0
• README.md:745 shields.io badge: version-3.2.0- → version-3.3.0-
• uv.lock: mempalace 3.0.0 → 3.3.0 (plus resolved dev/extras that were previously unlocked)

CHANGELOG cleanup

Pre-existing drift: v3.2.0 was tagged on 2026-04-12 but the CHANGELOG's [Unreleased] — v3.2.0 (on develop) header was never flipped to a dated release section. Fixed in this PR.

• Close out the old [Unreleased] block as ## [3.2.0] — 2026-04-12 (unchanged content — matches what shipped in the tag)
• Add a fresh ## [Unreleased] — v3.3.0 (on develop) section curated from the 49 commits since v3.2.0:
  • New features: closet layer (feat: closet layer — searchable index pointing to drawers #788), BM25 hybrid search (fix(search): hybrid closet+drawer retrieval — closets boost, never gate #795, feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), entity metadata (feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), diary ingest (feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), cross-wing tunnels (feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), drawer-grep (feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), offline fact checker (feat(v3.3): land Milla's stacked closet/BM25/KG/LLM chain (#784-#795) on develop #829), LLM closet regen (feat: optional LLM-based closet regeneration — bring-your-own endpoint #793), hall detection (fix: README audit — 42 TDD tests + hall detection + 7 claim fixes #835)
  • Bug fixes: cosine distance (Fix: set cosine distance metadata on all collection creation sites #807, Collection created without hnsw:space=cosine causes negative similarity scores #218), multi-agent file locking (fix: file-level locking to prevent multi-agent duplicate drawers #784, chore: forward closet layer (#788) into develop #826), hook chat noise (fix: stop hooks from making agents write in chat — save tokens #786), drawer hygiene (fix: strip system tags, hook output, and Claude UI chrome from drawers #785), diary ID collisions (fix: use microsecond timestamp and full content hash in diary entry ID #819), README audit (fix: README audit — 42 TDD tests + hall detection + 7 claim fixes #835), and more
  • Plus improvements, docs, and internal categories
• Adopt Keep a Changelog + SemVer framing at the top
• Add version-compare reference links at the bottom ([Unreleased], [3.2.0], [3.1.0], [3.0.0])
• Fix stale milla-jovovich/mempalace preamble URL → MemPalace/mempalace

What this PR intentionally does not touch

• Plugin manifests (.claude-plugin/, .codex-plugin/) — they're on a separate version track at 3.0.14 with their own chore: bump version to … commits. Not conflating the tracks.
• Other stale milla-jovovich/* URLs still in README and pyproject.toml — out of scope for a version bump; belongs in a dedicated URL-hygiene PR (pyproject.toml still points to old repo owner in project URLs #787 and docs: fix stale org URLs in website and plugin manifests (#787) #808 covered the website and contributor docs; README badges/links were missed).

Test plan

• uv run pytest tests/ --ignore=tests/benchmarks — 862 passed
• test_readme_claims.py — all 42 claim tests pass (version badge matches, pyproject matches, pyproject.toml label matches)
• uvx --from 'ruff>=0.4.0,<0.5' ruff check . — clean
• uvx --from 'ruff>=0.4.0,<0.5' ruff format --check . — 77 files already formatted