v0.23.3

Documentation release: no behavioural change from 0.23.2. The plugin code and skill instructions are identical; what ships is the user-facing description of the product→architect handoff that 0.23.0–0.23.2 built. All three plugins (product, architect, scalardb) move to 0.23.3 together.

Changed

• The user-facing docs now describe the handoff the code enforces. 0.23.0–0.23.2 turned the
  product→architect boundary into a contract with real invariants, but README.md and the getting
  started guides still showed it as a single arrow — a reader had no way to know that NFR- IDs
  are reused verbatim, that FEAT-→FR- links are recorded, that three things are left
  unanswered by design, or that both pipelines then share three files under work/. README
  gained a crosses/stays-behind table, both getting-started guides gained a "what the handoff
  actually does" section, and both architect input-requirements guides gained the three points
  that are easy to miss: a partial product run still hands off, Open Questions are one store, and
  new IDs are allocated from the graph. docs/design.md remains the contract; these are the
  doorways into it.