Maestro compat: numeric option fields accept `${VAR}` lookup interpolation (extendedWaitUntil.timeout, tapOn.index, siblings)

[thymikee]

Context

Numeric option fields on advertised commands currently demand a literal and reject ${VAR} — so an idiomatic env-driven flow dies on a command we support. The engine resolves ${VAR} lookups everywhere else (config/env/runFlow env/runScript output.*); this extends the same lookup to numeric fields, validating the resolved value with the existing rules (integer, range) and failing loud with the source line when the resolved value isn't a valid number.

Scope: variable lookup only. ${0 + 1}-style JS expressions are NOT this issue — that's the #1292 decision. After this lands, upstream/032_element_index still diverges (its corpus value is an expression), but the lookup half of the class is closed and flow 042 goes green.

Fields

• extendedWaitUntil.timeout (corpus upstream/042_extended_wait: ${TIMEOUT} from a flow env block)
• tapOn.index
• audit for siblings while there: waitForAnimationToEnd.timeout, swipe.duration, eraseText.charactersToErase, repeat.times, retry.maxRetries — same lookup rule everywhere, one shared helper, not per-field branches.

Repro

• FLOW_DIVERGENCES['upstream/042_extended_wait'] in scripts/maestro-conformance/expected-divergence.ts

Acceptance

• 042 divergence entry removed; verifier classifies it identical; pnpm maestro:conformance green with no new divergences.
• 032 divergence entry updated to name only the expression case, referencing Decision: should Maestro ${} interpolation evaluate JS expressions (GraalJS parity) or stay lookup-only? #1292.