[no bump] Move technical docs to docs/, add icon and PNG export tool

README now carries the icon, TL;DR, description and features; the
technical sections live in docs/. tools/icon_png.py renders
images/icon.svg to a square PNG (512x512 by default, --resolution N).
plugin.json points at the plugin's own icon.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/device-and-adb.md

@@ -0,0 +1,32 @@
+# Device setup and ADB automation
+
+## Device prerequisites
+
+- exteraGram 12.5.1+.
+- In-app: Preferences → Plugins → enable the plugin engine, then enable developer mode.
+- USB debugging enabled, device authorized (`adb devices`).
+
+Release-build APKs disallow `adb run-as`, so you cannot `adb push` a file straight into the
+app's private plugin directory. The on-device **dev server** (`tools/devclient.py`,
+`scripts/deploy.sh`) is the actual install path — it talks to the running app over a TCP
+socket forwarded with `adb forward`, and the app writes the file into its own storage.
+
+## ADB automation
+
+All scripts live in `scripts/`, are runnable from any working directory, and honor the
+standard `ANDROID_SERIAL` env var for device selection.
+
+- `scripts/adb-connect.sh [--debug]` — starts adb, waits for the device, (re)creates the
+  `tcp:42690` port forward (and `tcp:5678` with `--debug`), pings the dev server.
+- `scripts/deploy.sh [--release] [--enable] [--no-connect]` — bundles, connects, writes the
+  plugin to the device, optionally enables it, reloads it.
+- `scripts/watch.sh [deploy args…]` — watches `src/` and `plugin.json`, redeploys on change
+  (uses `inotifywait` if available, otherwise polls).
+- `scripts/logs.sh [-c] [-t] [-g PATTERN]` — streams logcat for the running app (`-t` for the
+  raw Chaquopy stdio tags, `-g` to grep, `-c` to clear first).
+- `scripts/debug.sh start|stop [--platform vscode|pycharm]` — forwards the debugger port and
+  tells the dev server to start/stop the in-app debugger. Requires `debugpy` (vscode) or
+  `pydevd-pycharm` (pycharm) present in the app's Python runtime — add it to `requirements` in
+  `plugin.json` if it's missing.
+- `scripts/fetch-sdk-stubs.sh [--beta]` — downloads the latest SDK type stubs into `stubs/`
+  for editor autocomplete.