[Sync] adopt unified stow layout from the private repo

Mirrors the private dots tree at 900bdda: one shared base plus per-host
overlays, replacing the old flat .config/ layout (last synced 2026-06-28).

- packages: common/ gui/ wm/ lw/ fl/ + install.sh and bin/ tooling (dotsync,
  reconcile-hyde.sh)
- new README (layout, deploy order, HyDE dependency), plus ToDo.md and
  HYDE-UPDATE.md
- current HyDE waybar rig (layouts/, cava), pi agent extensions, claude/
  config, tmux, presenterm, aichat roles
- drops stale duplicates and generated cruft that should never have been
  tracked: the second top-level .pi/ copy, btop.log, zellij config.kdl.bak,
  fish_variables, nvim codecompanion.lua
- .pi/agent/auth.json is gitignored now; auth.json.example ships instead
- fl/ and wm/ hypr themes/ stay untracked (HyDE-generated per machine, per
  the root .gitignore)

common/.config/cava/shaders/spectrogram.frag

@@ -0,0 +1,53 @@
+#version 330
+
+in vec2 fragCoord;
+out vec4 fragColor;
+
+// bar values. defaults to left channels first (low to high), then right (high
+// to low).
+uniform float bars[512];
+
+uniform int bars_count;  // number of bars (left + right) (configurable)
+uniform int bar_width;   // bar width (configurable), not used here
+uniform int bar_spacing; // space bewteen bars (configurable)
+
+uniform vec3 u_resolution; // window resolution
+
+// colors, configurable in cava config file (r,g,b) (0.0 - 1.0)
+uniform vec3 bg_color; // background color
+uniform vec3 fg_color; // foreground color
+
+uniform int gradient_count;
+uniform vec3 gradient_colors[8]; // gradient colors
+
+uniform sampler2D inputTexture; // Texture from the first render pass
+
+vec3 normalize_C(float y, vec3 col_1, vec3 col_2, float y_min, float y_max) {
+  // create color based on fraction of this color and next color
+  float yr = (y - y_min) / (y_max - y_min);
+  return col_1 * (1.0 - yr) + col_2 * yr;
+}
+
+void main() {
+  // find which bar to use based on where we are on the y axis
+  int bar = int(bars_count * fragCoord.y);
+  float y = bars[bar];
+  float band_size = 1.0 / float(bars_count);
+  float current_band_min = bar * band_size;
+  float current_band_max = (bar + 1) * band_size;
+
+  int hist_length = 512;
+  float win_size = 1.0 / hist_length;
+
+  if (fragCoord.x > 1.0 - win_size) {
+
+    if (fragCoord.y > current_band_min && fragCoord.y < current_band_max) {
+
+      fragColor = vec4(fg_color * y, 1.0);
+    }
+  } else {
+    vec2 offsetCoord = fragCoord;
+    offsetCoord.x += float(win_size);
+    fragColor = texture(inputTexture, offsetCoord);
+  }
+}