Recover delayed Search Assist answers within one ask command

[variablenix]

Summary

Close a retry gap where an answer available after the initial Search Assist requests could only be retrieved by asking the same question again.

• Space initial lightweight attempts by 300 ms instead of immediately repeating them.
• If the provider chain misses, wait 500 ms and retry the original question once within the same command.
• Reserve a three-second recovery window when at least 12 seconds remain; preserve shorter configured deadlines and never extend the overall timeout.
• Keep successful replies on the fast path and retain existing provider fallbacks and success-only caching.

Verification

• Regression fixtures for both Mario and Toad kart questions: two empty replies followed by a delayed answer recover within one command.
• Tests cover bounded misses, cancellation, successful requests not retried, original-question preservation, and deadline reservation.
• go test -race ./..., go vet ./..., staticcheck, and diff checks.
• Live server checks returned Search Assist answers for both screenshot questions and the cost comparison; existing lookup smoke tests passed.

The live queries may already be cached upstream; deterministic delayed-response fixtures cover the first-miss recovery behavior. This fixes a concrete scheduling gap, not a guarantee of availability or a bypass of provider challenges.