The cross-model peer scripts rejected the claude CLI's `fable` alias, could
not verify a Fable (or any full-id) receipt, and pinned the Claude default
with a stale "Opus 4.8" comment. Accept `fable`, derive delimited family
prefixes for aliases and full ids so a correct run no longer logs a false
mismatch and a sibling generation still does, and pin the Claude peer to
`claude-opus-5`.
Add `cross_model_model` / `cross_model_effort` so a checkout can persist the
peer's model and reasoning effort; both are validated per route in the worker
and fail the pass closed rather than substituting. Unset keeps the editorial
mapping unchanged.
Fixes#1335
Claude-Session: https://claude.ai/code/session_01RfqLRrbnSUSYyU2RFjPgh1
Trevin Chow
fad942fb38