docs(world-id): improve agent integration workflow

[Takaros999]

This PR improves the World ID agent skill based on developer integration feedback.

• adds a readiness-first workflow that resumes from existing project and Portal state
• gates Face Check on app access and corrects MCP signing-key handling
• adds environment-aware testing, replay protection, recovery guidance, and evidence-based handoff
• keeps MCP optional and client-agnostic while preserving the existing skill metadata

[mintlify]

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Project	Status	Preview	Updated (UTC)
world	🟢 Ready	View Preview	Jul 15, 2026, 2:45 AM

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Project	Status	Preview	Updated (UTC)
world	🟡 Building	–	Jul 15, 2026, 2:44 AM

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Handle session nullifiers in the test checklist

When the selected path is the session/sign-in flow that this skill now advertises, IDKit v4 session responses use session_id for continuity and session_nullifier for per-proof replay protection rather than a top-level nullifier (as documented in world-id/4-0-migration.mdx). This checklist will make agents persist/replay the wrong field for session routes, so session integrations can either fail validation or ship without the intended replay protection.

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