BOT-1359: Continue onboarding after key import

[baxen]

Why

Importing an existing key during first-launch onboarding publishes a new identity before the setup page renders. The machine gate treated that identity switch as unevaluated and replaced onboarding with a permanent loading screen.

What

• Mark imported identities as intentional onboarding transitions before updating the identity cache
• Keep the machine flow mounted through the identity switch so runtime setup can continue
• Add first-launch key-import regression coverage

Risk Assessment

Low — scoped to explicit key imports while machine onboarding is active; cold-boot identity evaluation remains unchanged.

References

• Linear: https://linear.app/squareup/issue/BOT-1359/app-hangs-after-entering-an-existing-key-on-first-attempt
• pnpm check, pnpm typecheck, and pnpm build
• Playwright import scenarios: 3 passed
• Pre-push Rust suite had 3 transient Codex adapter probe failures; all 3 passed when rerun individually

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[baxen]

No blocking findings. I independently reproduced the claimed race by running the new regression against the base implementation: the import succeeded, then the machine flow was replaced by the permanent app-loading-gate; the same test passes at this head.

The ordering in this patch is the right boundary: import_identity has already parsed, persisted, and installed the key before continueWithIdentity(identity.pubkey) runs, and the continuation is registered before React Query synchronously publishes that identity. The bypass is exact-pubkey scoped, while reset/locked/lost/relaunch stages retain higher precedence and ordinary cold boots still have a null continuation marker and take the existing evaluation path.

I also traced the marker lifecycle. Although the ref is process-lifetime, I don't see a current stale-marker path that alters behavior: completion writes a key-scoped completion flag, reopen explicitly marks the current key evaluated, a second machine import replaces the marker, failures never set it, and relaunch remounts the hook. Other in-app imports use the community-scoped QueryClient rather than this outer machine gate.

Independent validation at 0da894b40:

• base-vs-head first-launch regression: base fails at the loading gate, head passes
• full identity-lost.spec.ts: 8/8 pass (normal first launch, lost/locked recovery, re-import, relaunch)
• extra focused scenarios: completion + reopen + reload, a second explicit import, and an injected backend import failure: 3/3 pass
• TypeScript build/typecheck pass

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