feat: chord editing prototype

feat: lazy device connections
feat: backup docs
feat: chord library pagination

docs/BACKUP.md

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+# Chara Backup Format, Version 1
+
+JSON Schema files: TBD
+
+Chara backups are serialized using JSON, in this general format:
+
+```json
+{
+  "charaVersion": 1,
+  "type": "..."
+}
+```
+
+The presence of the key `charaVersion` uniquely identifies the JSON file as a chara backup file and serves
+as a discriminator against other generic JSON files. This key is mandatory for that reason.
+
+## Type `layout`
+
+```json
+{
+  "charaVersion": 1,
+  "type": "layout",
+  "device": "one",
+  "layers": [[], [], []]
+}
+```
+
+Devices at the current point in time may be identified as either `lite` or `one`, more to come in the future.
+
+Layers are serialized as an array of `[layer1, layer2, layer3]` in the internal order of the key, each specifying
+an action code. Action codes of `0` are considered unassigned.
+
+## Type `chords`
+
+```json
+{
+  "charaVersion": 1,
+  "type": "chords",
+  "chords": [
+    [
+      [1, 2, 3],
+      [3, 4, 5]
+    ],
+    [
+      [6, 7, 8],
+      [9, 10, 11]
+    ]
+  ]
+}
+```
+
+Chords are serialized using a key-value mapping of chord action codes to actions.
+
+## Type `settings`
+
+```json
+{
+  "charaVersion": 1,
+  "type": "settings",
+  "settings": [0, 1, 3, 6]
+}
+```
+
+Settings are serialized as an array of the values in the way they appear on the device.