feat(desktop): onboarding polish — docked CTAs, backup key card, dot grid

[cynfria]

Summary

Polish pass over the desktop onboarding flow.

• Docked CTAs. Every step's primary/secondary CTAs dock to the bottom of the viewport via a portal (OnboardingFooter), clearing the transform-containment that traps position: fixed, with a scrim so scrolled content fades under them. Applies across the machine, relay, and community flows.
• Shared chrome. New OnboardingChrome (top-left Buzz mark + step-dots pagination), replacing OnboardingStepDots.
• Backup key card. The private key sits in a translucent white card (bg-white/50, 12px radius) with olive ink (--buzz-onboarding-backup-ink) on the key and the "never share" caption; 36px mono key via a nsec-key token; no layout shift on reveal (same-length mask). Copy now works whether or not the key is revealed.
• Dot grid on all onboarding pages.
• CTA label colors: chartreuse on the landing screen, light blue inside the steps.

The non-obvious bug (worth a look)

The masked key overflowed its container only in WKWebView — WebKit will not line-break a run of • (U+2022) even with word-break: break-all / overflow-wrap: anywhere, while Chromium breaks it fine. Our Playwright suite runs Chromium, so it never caught this. Fix: the mask joins its bullets with a zero-width space (a break opportunity WebKit honors), and the wrapping text is a plain block inside the flex item. Verified in the WebKit engine that both masked and revealed states wrap and stay inside the card. See NsecMaskedDisplay.tsx.

Testing

• desktop-check, desktop-test, desktop-tauri-test pass; pnpm check:px-text and pnpm run build clean.
• New onboarding-docked-cta-screenshots.spec.ts; identity-lost.spec.ts updated for the dot-grid background.
• Onboarding + identity-lost E2E suites pass.

🤖 Generated with Claude Code

[brow]

🤖 Review summary (approved — no blockers). Cross-posting from the Buzz review thread for the record.

What I checked (full diff, all 19 files, base 2494926, head 307263d):

• Docked CTA portal (OnboardingFooter) — sound design. Portal target is a sibling of the transformed step subtree, which correctly escapes the position: fixed containing-block trap. The animation-fill-mode: both → backwards change on the mask-reveal transition is the right companion fix (end state is identity transform, so no visual change). Inline fallback when no provider exists covers KeyringLockedScreen, and its full-width button styling is preserved via the variant branch.
• Enter-key double-submit guard in NostrKeyImportForm — good catch, real bug: the submit button became type="button" in the portal, but the single-field form still submits on Enter; the in-flight guard in handleSubmit prevents a concurrent double keyring write.
• WebKit mask wrap (NsecMaskedDisplay) — ZWSP-joined bullets is a legit fix for WebKit refusing to break U+2022 runs; mask is non-selectable and copy uses the raw nsec, so the ZWSP never leaks. Masking every char (vs the old 6-char plaintext prefix) is a strict improvement. Copy-while-masked is fine — clipboard gets the real key by explicit user action.
• Security invariants intact — nsec still not in DOM until reveal, select-none + blur while masked, variant="boxed" settings usage unaffected.
• Step-dots correctness — community flow correctly mirrors the render condition so the "finalizing" transient stays on page 6 (regression the branch itself caught and fixed); old OnboardingStepDots deleted with zero stale references.
• Tests — new docked-CTA screenshot spec wired into the smoke project; identity-lost spec updated to match the dot-grid background-image. All CI green (Desktop Core, Build, 4 smoke E2E shards, 2 integration shards).

One nit posted inline (non-blocking): desktop/src/shared/ui/step-progress.tsx is now dead code.

[brow]

🤖 Non-blocking nit: with this last import gone (the AvatarStep usage is also removed in this PR), desktop/src/shared/ui/step-progress.tsx is now dead code — nothing references StepProgress anymore. Fine to drop in a follow-up polish PR.