fix(wizard): report gateway failures before success summary (#691)

docs/scratchpads/B3-wizard-gateway-health-order.md

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+# B3 — Wizard completion ordering
+
+## Problem
+
+The wizard printed the success summary / `Mosaic is ready.` during `finalizeStage`, before the gateway configuration stage had completed its daemon health check. If the gateway health gate later failed, the user could see a success claim followed by a gateway failure.
+
+## Diagnosis
+
+`finalizeStage` handled both mutation work and terminal success messaging. Wizard paths then ran `gatewayConfigStage` and `gatewayBootstrapStage` afterward:
+
+1. finalize writes config, links runtime assets, syncs skills, runs doctor;
+2. finalize prints `Installation Summary` + `Mosaic is ready.`;
+3. gateway config starts/waits for daemon health;
+4. gateway bootstrap runs.
+
+The summary needed to be deferred until after the gateway readiness gates.
+
+## Fix
+
+- `finalizeStage` now returns a `showSummary()` callback and supports `deferSummary`.
+- Wizard/quick-start paths call finalize with `deferSummary: true`.
+- `showSummary()` is called only after gateway config reports ready and bootstrap completes, or immediately when the caller explicitly skips gateway setup.
+- If gateway health/config reports not ready, the wizard returns/aborts without printing the success summary.
+- Folded in adjacent runtime install hint fix for Pi: `curl -fsSL https://pi.dev/install.sh | sh`.
+
+## Verification
+
+- Added unified-wizard coverage for summary-after-health and no-summary-on-health-failure.
+- Targeted: `pnpm --filter @mosaicstack/mosaic test -- unified-wizard finalize-skills`
+- `pnpm format:check`
+- `pnpm typecheck`
+- `pnpm lint`
+- `pnpm build`
+- `pnpm test`
+- Codex code review: approve.
+- Codex security review: one low finding on the requested Pi `curl | sh` install hint; no security finding in the wizard completion-ordering change.