chore: prepare v3.12.0 release

[acidkill]

Summary

• Synchronize all 16 release-version fields to 3.12.0.
• Replace the README release highlights and add a complete 3.12.0 changelog entry for resumable, bounded consolidation and maintenance.
• Keep checkpoint-v1 as a stable compatibility epoch across package releases, allowing compatible unfinished v3.11 runs to resume after schema migration while preserving code/format/schema fences.

Why

This release groups the consolidation and maintenance improvements merged since v3.11.0. Matching the Python, plugin, npm, lockfile, and VS Code metadata prevents the release workflows from publishing mismatched versions. Keeping the checkpoint compatibility epoch separate from the package version avoids invalidating safe v3.11 checkpoints solely because the release number changed.

Changes

• Bump the 16 fields reported by scripts/pre_ship.py, including the pinned package-version test.
• Document durable checkpoints, bounded semantic discovery and maintenance, keyset scans, recovery fixes, and the schema-v12 checkpoint behavior.
• Keep the static 3.11.0:checkpoint-v1 marker unchanged across the package bump. A regression assertion protects this contract; incompatible marker, format, schema, and run-parameter states remain fenced off.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Tests

Test plan

• pytest tests/ -m "not stress" -n auto — 7,686 passed, 231 skipped, 1 xfailed on the package/docs head.
• Focused checkpoint and migration tests after compatibility fix — 53 passed.
• Full pre-ship gate after compatibility fix — all checks pass with dev/server test extras.
• ruff check src/ tests/ and ruff format --check src/ tests/.
• mypy src/ --ignore-missing-imports.
• python scripts/pre_ship.py --only versions --expect v3.12.0.
• Generated MCP/CLI documentation freshness checks pass.
• GitHub CI run 36121863691 passes, including SurrealDB integration, Python 3.11 and 3.12 tests, documentation, lint, type-check, security, version parity, dashboard tests/build, and Python package build.

Testing

The local suite ran with external database credentials unset; live database tests were skipped locally. GitHub CI on the final head passed the isolated SurrealDB integration, including the v3.11 checkpoint-resume regression coverage.

Checklist

• My changes follow the project style guidelines
• I have performed a self-review
• I updated the pinned version test
• I updated the documentation and CHANGELOG.md
• No AI attribution or unrelated files are included

Verified by

@acidkill

Related Issues

None