v0.26.8

Patch release for processkit issue cleanup.

Fixes

• pk-doctor id_vocabulary now validates configured kind palettes
  instead of warning on the unconfigured default two-word pool. This
  resolves the structurally unresolvable
  id-vocabulary.default-pair-capacity-low warning.
• scripts/processkit-diff.sh now emits normalized affected_files
  rows in JSON and TOML output so migration generators can populate
  Migration frontmatter from the same structured source used for body
  rows.

Validation

• uv run scripts/smoke-test-servers.py
• npm --prefix docs-site run build
• scripts/check-src-context-drift.sh --release-deliverable
• pk-release-audit on src-context
• release tarball checksum verified