feat(theme): make Boreal the distro default

Seed theme-state.json and the downstream template from themes/boreal.json
(including border + empty settings). Point eval/schema fallbacks at Boreal
(theme.nix preset, plymouth and live-ISO splash colors, theme-shot, sync
error examples). Docs/TESTING and RECOVERY follow the new default.

Verified: state matches boreal palette; theme-contrast all pass.
preview.png for boreal still missing (picker plain-name; V3 capture).

docs/VISION.md

@@ -37,7 +37,7 @@ judgment; agents prepare, do not advance `v1`):
 | Bar | Done looks like |
 |-----|-----------------|
 | **Install golden path** | Offline (or documented online) install → first boot themed desktop; swap=0 and unattended LUKS contracts correct |
-| **Default identity** | Boreal (or chosen default) is the seed theme; picker has preview |
+| **Default identity** | Boreal is the seed theme (shipped 2026-07-09); picker should have `preview.png` |
 | **Day-2 confidence** | Doctor covers real failure modes; firmware and fingerprint are discoverable without reading the README |
 | **Hardware story** | `docs/HARDWARE.md` matches code; option-docs green; i2c/ddcci documented |
 | **Honesty** | No “done” claims past verified tier; HARDWARE-QUEUE cleared or consciously deferred |