docs: approved UX-modes design (View/Plan/Devices tabs) — docs/UX-MODES.md + ROADMAP phase 11

Research only, no product changes. Confirms and structures the owner's mandate
(view mode must be display-only) and issue #3 feedback; lists deprecations and
approved follow-up features with implementation iterations.

docs/UX-MODES.md

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+# UX redesign: three modes (approved 2026-07-21)
+
+> Approved design for reorganizing all card interactions into three tab-like modes.
+> Driven by the owner's mandate and confirmed by real user feedback
+> ([issue #3](https://github.com/Matysh/houseplan-card/issues/3): *"When moving the
+> map around, I sometimes move the doors/sensors around"*). This document is the
+> source of truth for the implementation iterations below. No code has been changed yet.
+
+## Principle
+
+A segmented control in the card header with three tabs; the active one is visually
+highlighted, and edit modes add a colored frame around the stage so the mode is
+obvious at a glance:
+
+**[ 👁 View ] [ 📐 Plan ] [ 🔧 Devices ]**
+
+- **View** is the default and the only mode after every load (edit modes are never
+  restored across reloads).
+- **Plan** and **Devices** are shown only to admins when `admin_only` is on.
+
+## View — display and device interaction only
+
+Allowed: pan/zoom (wheel, pinch, buttons), switching spaces, device tap
+(info / more-info / toggle per settings), long-press → info card, opening tap →
+door/lock info card, room tap → HA area, hover tooltips (name, temperature, signal).
+
+Removed from this mode (they move, not die):
+- icon dragging ("drag anywhere", v1.9 — consciously reversed),
+- room-label dragging,
+- opening dragging along walls and double-click properties (v1.23.1),
+- every edit button in the header (+device, 👁 show-all, ↺ reset, ⬡ rules, ⚙ general,
+  per-space gear, markup toggle).
+
+Header in View: space tabs, device count, zoom cluster. Nothing else.
+
+## Plan — geometry and appearance of the space
+
+- Toolbar tools: Outline room, Delete room, Merge, Split, Opening (place / drag along
+  walls / properties), Room labels (drag positions — labels are part of the plan).
+- Space gear dialog (title, plan image / hand-drawn, scale, Display section, show_lqi),
+  add space, floors import, delete space.
+- ⚙ General settings (fill palette) lives here — it is about the plan's appearance.
+
+## Devices — placement and marker configuration
+
+- Icon dragging (ONLY here). Click on a device opens the **edit dialog directly**
+  (binding, name, icon, size/angle, display badge/ripple + colors, tap override,
+  model/link/description/PDFs, room).
+- + add device/entity/virtual, hide device, ↺ reset layout, 👁 show-all (curation
+  tool), ⬡ icon rules.
+
+## Deprecations decided
+
+1. "Drag anywhere" (v1.9) — reversed by this design.
+2. Opening drag / dbl-click properties in view (v1.23.1) — moved into Plan.
+3. The markup toggle button — replaced by the Plan tab.
+4. Legacy localStorage mode (card without the integration) — candidate for removal
+   in the next major; adds branching for a half-working scenario.
+
+## Approved follow-up features (from issue #3, by priority)
+
+1. State-reflecting icons (open/closed door variants etc., like core HA).
+2. `display: value` — show the measurement instead of an icon.
+3. Light color in the icon/ripple (RGB lights).
+4. Alarm visual (leak/smoke/doorbell): red pulse overlay.
+5. Rooms as sub-areas without an HA area + manual device placement by room id.
+6. Backlog (not planned): music notes for players, directional TV ripples.
+
+## Implementation iterations
+
+- **It.1 — mode shell:** the segmented control, mode state, View-mode gating of all
+  edit interactions/buttons (biggest UX win, smallest surface).
+- **It.2 — Plan tab:** move markup tools + space dialogs + labels drag + openings
+  editing under Plan; colored frame indicator.
+- **It.3 — Devices tab:** drag + direct-edit click + curation tools under Devices.
+- **It.4+:** follow-up features 1–5 above, each its own release.