Build verified; add icon-generator tool and install/README notes

- ./gradlew assembleDebug produces a 13 MB arm64-v8a APK (libtsjet/libllama/
  libggml/libc++_shared bundled; JNI compiles cleanly against llama.cpp b10333)
- Add tools/gen_launcher_icons.py so the launcher icon is reproducible from art
- README: mark build verified, add sideload/install section

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/gen_launcher_icons.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+"""Regenerate Android launcher icons from piti-icon.png.
+
+Usage:  python3 tools/gen_launcher_icons.py
+Requires: Pillow  (pip install Pillow)
+
+Produces, under app/src/main/res/:
+  - mipmap-<dpi>/ic_launcher.png          legacy square (rounded), all densities
+  - mipmap-<dpi>/ic_launcher_round.png    legacy round, all densities
+  - mipmap-<dpi>/ic_launcher_foreground.png  adaptive-icon foreground (padded)
+The adaptive XMLs (mipmap-anydpi-v26/) and the black background drawable are
+checked in and don't need regenerating.
+"""
+import os
+from PIL import Image, ImageDraw
+
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+SRC = os.path.join(ROOT, "piti-icon.png")
+RES = os.path.join(ROOT, "app", "src", "main", "res")
+BG = (0, 0, 0, 255)  # matches the app's black theme / ic_launcher_background.xml
+
+brain = Image.open(SRC).convert("RGBA")
+
+LEGACY = {"mdpi": 48, "hdpi": 72, "xhdpi": 96, "xxhdpi": 144, "xxxhdpi": 192}
+ADAPTIVE = {"mdpi": 108, "hdpi": 162, "xhdpi": 216, "xxhdpi": 324, "xxxhdpi": 432}
+
+
+def fit(img, box):
+    w, h = img.size
+    s = box / max(w, h)
+    return img.resize((max(1, int(w * s)), max(1, int(h * s))), Image.LANCZOS)
+
+
+def rounded_mask(size, radius):
+    m = Image.new("L", (size, size), 0)
+    ImageDraw.Draw(m).rounded_rectangle([0, 0, size - 1, size - 1], radius=radius, fill=255)
+    return m
+
+
+def circle_mask(size):
+    m = Image.new("L", (size, size), 0)
+    ImageDraw.Draw(m).ellipse([0, 0, size - 1, size - 1], fill=255)
+    return m
+
+
+def compose(size, mask, content_scale):
+    canvas = Image.new("RGBA", (size, size), BG)
+    fg = fit(brain, int(size * content_scale))
+    canvas.paste(fg, ((size - fg.width) // 2, (size - fg.height) // 2), fg)
+    out = Image.new("RGBA", (size, size), (0, 0, 0, 0))
+    out.paste(canvas, (0, 0), mask)
+    return out
+
+
+def save(img, folder, name):
+    d = os.path.join(RES, folder)
+    os.makedirs(d, exist_ok=True)
+    img.save(os.path.join(d, name))
+
+
+for bucket, size in LEGACY.items():
+    save(compose(size, rounded_mask(size, int(size * 0.18)), 0.86), f"mipmap-{bucket}", "ic_launcher.png")
+    save(compose(size, circle_mask(size), 0.86), f"mipmap-{bucket}", "ic_launcher_round.png")
+
+for bucket, size in ADAPTIVE.items():
+    fg_canvas = Image.new("RGBA", (size, size), (0, 0, 0, 0))
+    fg = fit(brain, int(size * 0.64))  # keep within the adaptive-icon safe zone
+    fg_canvas.paste(fg, ((size - fg.width) // 2, (size - fg.height) // 2), fg)
+    save(fg_canvas, f"mipmap-{bucket}", "ic_launcher_foreground.png")
+
+print("launcher icons regenerated under app/src/main/res/")