feat: add theme-lab — turn any image into a Hermes Desktop theme

[0-CYBERDYNE-SYSTEMS-0]

What

Adds theme-lab — the first desktop-surface example in this repo. A Hermes Desktop plugin that turns any image into a full DesktopTheme (light + dark palettes, 16-color ANSI terminal palette), registered via THEMES_AREA so it appears live in Settings → Appearance, ⌘K, and /skin.

Why this belongs here

Per the repo README: "Reference plugins live here so plugin authors can read them, copy them, install them as user plugins" — and "These are not bundled with hermes-agent." This is exactly that: a focused, self-contained desktop plugin referencing the Desktop Plugin SDK. It is the first THEMES_AREA example in the repo (the existing examples are Python gateway/dashboard plugins that install to ~/.hermes/plugins/; a desktop plugin lives in ~/.hermes/desktop-plugins/ — a different SDK surface, documented in the README).

SDK surfaces it demonstrates

• THEMES_AREA — register a DesktopTheme (colors + darkColors + ANSI terminal/darkTerminal).
• PANES_AREA + PALETTE_AREA — the forge pane and a ⌘K command.
• ctx.storage — persistence with a v1 → v2 schema migration.
• Live apply without Settings — the app has no SDK API to set the active skin, but the gateway config.set display.skin=<name> RPC broadcasts skin.changed, which the desktop drains into a live repaint. The plugin writes the forged theme as a backend skin (~/.hermes/skins/<slug>.yaml) so the gateway can resolve it, then applies it live — no Settings visit.
• Boot persistence — re-applies the saved appearance once the gateway is ready (the desktop hydrates the saved skin before plugin/backend themes exist, so it would otherwise snap to default).

How to install / test

cp -r theme-lab ~/.hermes/desktop-plugins/

The app hot-loads within seconds; ⌘K → Reload desktop plugins if it doesn't appear. Open the Theme Lab pane, drop an image, hit Apply — the theme applies live.

Notes

• Standalone distribution (full history + issues): 0-CYBERDYNE-SYSTEMS-0/theme-lab. This example is pinned to that work.
• Zero dependencies — pure-ESM plugin.js, only imports @hermes/plugin-sdk + react. Color math validated by a standalone Node harness (forge-math-test.cjs, no build).
• Size note: at ~1690 LOC this is a complete, production-shaped plugin rather than a stripped ~200-LOC stub — it demonstrates the SDK end to end with real error handling, persistence, and migration. If reviewers would prefer a minimal single-surface version, I'm happy to trim.
• Known limitation (documented in README + code): the live-apply backdoor writes to ~/.hermes/skins/ and requires the gateway; if unavailable it falls back to the honest Settings deep-link.

License

MIT (same as this repo).