feat: route review children through logical model

[BakerSean168]

Summary

• bump the single ForgeFlow runtime dependency to pi-subagents@0.75.0
• hard-cut forgeflow.review and forgeflow.accept to the stable forgeflow/reviewer virtual model
• bump both trusted workflow resource versions to v4
• remove the temporary 0.74 virtual-child compatibility note
• document that physical reviewer selection remains operator policy below the logical role

Upstream dependency evidence

pi-subagents@0.75.0 includes the two released child-runtime fixes ForgeFlow was waiting for:

• #2636: flush queued virtual-model registrations in child sessions
• #2638: verify virtual-model children against their logical selection rather than dispatched physical response model

Verification

• npm run check: 47/47 passed
• npm pack --dry-run: passed
• installed dependency resolves exactly to pi-subagents@0.75.0
• installed package contains the virtual-child selection verification path
• git diff --check: passed