v0.25.6 - Provider-neutral pk command projections

v0.25.6 is a patch release that makes processkit command exposure
provider-neutral and closes the remaining dogfood v2 backlog audit gap.
Slash-capable harnesses continue to receive pk-* command projections,
while non-slash harnesses receive matching natural-language skill
adapters.

Added

• Added provider-neutral command projection for
  pk-explain-routing. The model-recommender command now has a
  canonical command file, Claude slash projection, Codex skill shim, and
  MCP metadata entry.

Changed

• Processkit command metadata now treats pk-* as mandatory.
  pk-doctor validates canonical command files, Claude projections,
  Codex skill projections, argument hints, and projection-only command
  drift across all processkit skills.
• Renamed team-creator commands into the reserved namespace.
  The former team-create, team-rebalance, and team-review
  command files are now projected as pk-team-create,
  pk-team-rebalance, and pk-team-review.
• Dogfood backlog entities were restamped to the v2 API contract.
  The live context/ tree no longer carries legacy v1 backlog entities
  that made full release-audit output noisy outside the shipped
  src/context/ boundary.

Verification

• pk-doctor reported 0 ERROR / 0 WARN / 19 INFO.
• pk-release-audit --tree=context reported 0 ERROR.
• pk-release-audit --tree=src-context reported 0 ERROR / 0 WARN.
• uv run scripts/smoke-test-servers.py passed across the MCP smoke
  suite.
• uv run context/skills/processkit/pk-doctor/scripts/test_doctor.py
  passed.
• npm --prefix docs-site run build passed.

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