libptouch: P700/P900 families, optional JSON config, ESC i z and print sequencing

- Add printer_family and profile flags; load overrides from printer_families.json
- Set ESC i z page byte from profile; pass prof into ptouch_fill_esc_iz
- End print with 0x1A only (drop FF prefix); extend Ruby FFI and CLI media info
- Add reference/ptp_raster_ref.adoc; install config under share/ptouch_label

Made-with: Cursor

config/printer_families.json

@@ -0,0 +1,18 @@
+{
+  "families": {
+    "p700": {
+      "comment": "PT-P750W / PT-P710BT（cv_ptp750w_710bt_jpn_raster_102.pdf 系）",
+      "print_dpi": 180,
+      "margin_feed_dpi": 180,
+      "margin_feed_max_dots": 900,
+      "send_esc_ia_cut_each": false
+    },
+    "p900": {
+      "comment": "PT-P900 / P900W / P950NW / P910BT（cv_ptp900_jpn_raster_102.pdf 系）",
+      "print_dpi": 360,
+      "margin_feed_dpi": 360,
+      "margin_feed_max_dots": 1800,
+      "send_esc_ia_cut_each": true
+    }
+  }
+}