feat: first-run setup wizard

[JiLiZART]

First run now offers where the vault comes from, instead of only offering to create one.

• Shared UI — a wizard (packages/ui/src/components/setup-wizard.tsx) driven by a host-supplied SetupBackend; the old SetupView is its create step. Hosts declare what they can offer, so the wizard renders only choices that can complete.
• Import adopts — the chosen file becomes this device's vault and its passphrase becomes this device's passphrase. New AppVault::adopt_blob + adopt_vault command on desktop, ExtensionVaultService.adoptBlob in the extension. Both refuse once a vault exists; import_blob still merges for the Settings path.
• Desktop — after the vault exists, an optional step turns on the bridge and shows a pairing code. Skipping leaves the bridge off.
• Extension — a third starting point pairs with the desktop and picks client or sync, so the mode is chosen rather than defaulting silently. Nothing is written unless pairing succeeds.
• Also carries the changeset.yml exemption for the release PR (see openspec/changes/fix-release-pr-flow/), which is why the check currently fails on chore: Release 0.1.1 #3.

Planning artifacts: openspec/changes/add-first-run-setup-wizard/.

Verified: cargo test 79 pass, pnpm -r test 188 pass, pnpm -r typecheck clean, i18n catalogs in sync. cargo clippy -D warnings fails only on the pre-existing time_sync.rs:83 drift.

Not verified headlessly: the desktop tray/popup run-through and the end-to-end pairing across both wizards.

[github-actions]

✅ Changeset detected

.changeset/first_run_setup_wizard.md

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default: minor
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# First-run setup wizard

A fresh install now asks where your vault should come from instead of only
offering to create one: start a new vault, import a vault file you exported
elsewhere, or — in the extension — use the vault in the desktop app. Importing
on first run adopts the file, so the passphrase that opens it unlocks this
device too. After creating a vault the desktop app offers to turn on the browser
bridge and show a pairing code.

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	2fau	a23d46c	Commit Preview URL Branch Preview URL	Sep 20 2026, 06:53 PM