Umsetzungsplan mit 13 Phasen anlegen und in AGENTS.md verlinken

Schrittweiser Plan fuer alle offenen Punkte inkl. Abnahmekriterien je
Schritt, Nachschlagereferenz und Definition of Done. Ergaenzt die
Entscheidungen vom 2026-08-11: kein Electron (Capacitor bzw. PWA) und
kein eigenes Backend (HA-API direkt).

AGENTS.md

@@ -66,10 +66,12 @@ assets. Never mix these the other way around.
 
 **Reading order for a new session:**
 1. This file (overview + open items)
-2. `SPECIFICATION.md` — authoritative for the HA panel, incl. §7 "Known Gaps"
-3. `COMPANION_APP_ARCHITECTURE.md` — authoritative for DataMetric360 (decided, barely built)
-4. `AUDIT_2026-08-10.md` — accessibility/platform audit of the panel (partly done, rest below)
-5. `bauauftrag.md` — **historical only**; code has diverged (see SPECIFICATION.md §7)
+2. `UMSETZUNGSPLAN.md` — the step-by-step execution plan for all open items (13 phases with
+   commands and acceptance criteria); when working on an open item, follow the plan's phase
+3. `SPECIFICATION.md` — authoritative for the HA panel, incl. §7 "Known Gaps"
+4. `COMPANION_APP_ARCHITECTURE.md` — authoritative for DataMetric360 (decided, barely built)
+5. `AUDIT_2026-08-10.md` — accessibility/platform audit of the panel (partly done, rest below)
+6. `bauauftrag.md` — **historical only**; code has diverged (see SPECIFICATION.md §7)
 
 ## The three projects in this repo
 
@@ -172,6 +174,11 @@ capacitor/iframe/browser (`umgebung.ts`), types + entity table (`types.ts`), fac
 
 ## Open items
 
+Execution order, exact steps, and acceptance criteria for every item below live in
+`UMSETZUNGSPLAN.md` (phases 1–13). Additional decisions of 2026-08-11: **no Electron** (Capacitor
+wraps the web app for iPhone; a PWA home-screen install is the accepted intermediate step) and
+**no separate backend** (the app talks to the HA REST/WebSocket API directly).
+
 ### A) Build DataMetric360 (the big block)
 
 - [ ] Fix the Claude Design draft (RS 4, not RS 6) and extend it by the 16 missing sub-pages;