Request companion library consent before smart caching

[misantronic]

Consumes the per-caller consent flow proposed in ARMSX2/ARMSX2#616.

• Smart caching now stops before caching anything when a companion still needs consent, prompts, and then runs once. Previously a full caching pass ran first and the user was asked afterwards about data that run had already finished without, then sat through a second pass to use it.
• Distinguishes "you may not read this" from "nothing was played" using the provider's cursor extras — both are an empty cursor otherwise.
• Honours a refusal the emulator already recorded, so the prompt does not reappear on every run.
• Stores no consent state on this side. An earlier revision persisted the refusal here and it went stale the moment the user changed their mind in the emulator without a run in between; the emulator owns both the switch and the prompt, so it is the only place that can track this correctly.

Requires the upstream change to ship; inert until then.

Verified end-to-end on-device: prompt appears before caching, Allow leads to a single pass that includes PS2 titles, Deny is respected silently on later runs, and toggling sharing in the emulator makes it ask again.

Tracked in #33.