feat v1.19.0: a line is never an entity of its own — walls are derived from rooms

A wall can only exist as an edge of a closed room:
- roomEdges(rooms) derives walls from room outlines, deduping shared ones, so deleting a
  room keeps the borders its neighbours still contribute and drops the rest — the rule
  falls out of the model instead of needing bookkeeping.
- Nothing is persisted while drawing: an outline you never close leaves no lines behind
  (previously every click pair was written to space.segments immediately).
- The 'Erase line' tool is gone; space.segments is stripped on every save (validation
  still tolerates it on read so a stale tab cannot fail a save).
- Dead code out: _addSegment/_removeSegmentByKey/_distToSeg/_pathSegs/_segKey.
Docs (ARCHITECTURE/TESTING/CHANGELOG) updated in the same commit. +2 tests (63).

custom_components/houseplan/const.py

@@ -11,7 +11,7 @@ PLANS_DIR = "houseplan/plans"  # relative to the HA configuration directory
 FILES_URL = "/houseplan_files/files"
 FILES_DIR = "houseplan/files"
 CONF_ADMIN_ONLY = "admin_only"
-VERSION = "1.18.1"
+VERSION = "1.19.0"
 
 DEFAULT_CONFIG: dict = {
     "spaces": [],

custom_components/houseplan/diagnostics.py

@@ -31,7 +31,6 @@ async def async_get_config_entry_diagnostics(
                 "has_plan": bool(s.get("plan_url")),
                 "rooms": len(s.get("rooms", [])),
                 "rooms_with_area": sum(1 for r in s.get("rooms", []) if r.get("area")),
-                "segments": len(s.get("segments", [])),
             }
             for s in config.get("spaces", [])
         ],

custom_components/houseplan/manifest.json

@@ -16,5 +16,5 @@
   "issue_tracker": "https://github.com/Matysh/houseplan-card/issues",
   "requirements": [],
   "single_config_entry": true,
-  "version": "1.18.1"
+  "version": "1.19.0"
 }

custom_components/houseplan/validation.py

@@ -100,6 +100,9 @@ SPACE_SCHEMA = vol.Schema(
         vol.Required("aspect"): vol.All(vol.Coerce(float), vol.Range(min=0.05, max=20)),
         vol.Required("view_box"): vol.All([vol.Coerce(float)], vol.Length(min=4, max=4)),
         vol.Required("rooms"): [ROOM_SCHEMA],
+        # Legacy: walls are derived from room outlines since v1.19.0 — a line has no
+        # independent existence. Still accepted so a stale browser tab cannot fail a save;
+        # the card strips the field on every write.
         vol.Optional("segments"): [vol.All([vol.Coerce(float)], vol.Length(min=4, max=4))],
     },
     extra=vol.ALLOW_EXTRA,