v0.6.0: Add support for UIX fork

[v0.6.0] — 2026-07-03

Adds first-class support for UIX, the
card-mod-derived HA integration, alongside card-mod — read, generate, and
warn about cross-compatibility correctly regardless of which one (or neither)
is installed. Verified against real running instances of both engines in
Docker (tools/sandbox/run.sh and tools/sandbox/run-uix.sh), not just
source-reading or unit tests. Fixes #20.

Added

• UIX detection — isUixInstalled() probes for UIX's uix-node custom
  element, independent of the existing card-mod probe. The "card-mod not
  detected" warning now only shows when neither engine is found.
• Reads uix: style blocks with the same uix: > card_mod: precedence
  UIX itself uses, so a card styled under uix: (by hand, or by UIX's own
  tooling) reads back correctly into the panel — including entities-card
  rows, which carry independent card_mod:/uix: blocks from the card
  itself.
• Generates the right key automatically — output stays card_mod: by
  default (UIX fully supports it as a fallback), switching to uix: only
  when UIX is installed and card-mod is not. This mirrors a real constraint:
  UIX's own installer refuses to set up alongside a card-mod.js Lovelace
  resource, so "both installed" isn't a state its own tooling lets you reach
  — defaulting to card_mod: whenever card-mod is present is the safe
  choice, not a guess.
• Reverse-compatibility warnings — if a card's styling (or an individual
  entities-card row's) lives only under uix: and UIX isn't installed, the
  panel warns about that specific card/row instead of silently rendering
  unstyled, with a one-click "copy to card_mod" fix for plain CSS. uix:
  content using macros/billets gets a clear incompatibility warning instead
  (worded differently depending on whether card-mod or UIX is the active
  engine) — those features have no card-mod equivalent and can't be safely
  regenerated by the studio, so there's no valid "fix" to offer, just a
  heads-up.
• UIX sandbox (tools/sandbox/run-uix.sh) — a second Dockerised HA rig
  running a real UIX integration, set up headlessly through its actual config
  flow. Verifies detection, both style keys, uix:-over-card_mod:
  precedence, and the live editor's output key against the real integration.
  tools/sandbox/harness/compat_check.mjs covers the reverse direction
  (card-mod-only) against the existing card-mod sandbox.

Correctness details worth knowing

• Clearing a style clears it under both keys. If you clear all styling on
  a card that has stale content under the other key (e.g. old card_mod:
  from before you switched to UIX-only), that stale value is cleared too —
  otherwise it would silently reactivate via whichever engine's fallback
  precedence applies, so "clear" wouldn't actually mean no styling.
• Editing card_mod: keeps a plain uix: value in sync (UIX prioritizes
  uix: over card_mod:, so without this a card_mod edit could silently
  have no visible effect under UIX) but never touches a uix: block using
  macros/billets — that's hand-authored content the studio can't safely
  regenerate, so it's left untouched rather than silently overwritten. An
  info banner explains when this applies.
• Editing uix: directly does overwrite existing macro/billet content,
  since (unlike the case above) there's no fallback key to preserve it in —
  the panel warns about this before it happens rather than silently
  proceeding or silently doing nothing.
• Explicit-but-empty style values (uix: {style: ''} or {style: {}}) are
  treated as "not set," matching UIX's own effective behavior, so they can't
  accidentally mask a real card_mod: fallback.