remaining-groups-move-into-the-register

[VeryComplexAndLongName]

Move the eight remaining message groups — HRN, AGT, TSK, VAL, ARC, WSP, KEY and NET — into the message register, so every message the product says to a person is said by its OSW-<GROUP>-<NNN> identifier from the one register in core.

What changes

• packages/core/src/message-register.ts gains entries for all eight groups (~200 new identifiers); say/withMessageCode remain the single surface.
• Every carrier that says a sentence now carries its code: reason: fields, refused(...), the describe* formatters, and the refusal error classes (InvalidHarnessConfigError, ForgeRefusal, EnrolmentRefusedError, JoinRefusedError, the server's Refused, the CLI's ReportRefusal).
• The said-in-place ratchet in message-register.test.ts is widened from four carriers to every carrier, and re-baselined down to 330 (the documented residual of messages not yet in the register).
• docs/messages.md regenerated; openspec/specs/messages/spec.md updated.
• Adapters (cli, extension, server) surface the identifier instead of their openspec-ui-cli: / OpenSpec Workbench: prefixes where a core refusal has a code.

Checks

• npm run typecheck clean; npm run lint 0 errors.
• core 2298 passed, cli 285, extension 538, server 135, webui 768 (three flaky timing/git-lock failures pass in isolation).
• openspec validate remaining-groups-move-into-the-register --strict valid.
• No dead register identifiers remain (every registered code is said by some source site).