Add braille renderer with amber demo GIF

- Braille canvas: 2×4 dots per cell (4× resolution vs half-blocks)
- Shared palettes, effects, and audio between both renderers
- README with both demos and build instructions for each

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -2,14 +2,20 @@
 
 A terminal-based oscilloscope with CRT phosphor physics, written in Nim. Zero dependencies — 200KB binary, just libc.
 
+## Half-block renderer
+
 ![demo](demo.gif)
 
+## Braille renderer (amber palette)
+
+![braille demo](braille_demo.gif)
+
 ## Features
 
 - **CRT boot/shutdown animations** — phosphor ramp, beam sweep, vertical collapse, dot fade
 - **Y-T and X-Y modes** — time-domain waveform or Lissajous figures
 - **Phosphor persistence** — beam bloom, decay trails, intensity-based shading
-- **Half-block rendering** — 2x vertical resolution using Unicode `▀▄█` characters
+- **Two renderers** — half-block (`▀▄█`) or braille dots for 4× resolution
 - **Live audio capture** — direct libav bindings via dlopen, zero install
 - **Threaded audio** — 60fps rendering, audio capture on separate thread
 - **6 CRT phosphor palettes** — green, amber, cyan, blue, white, red
@@ -21,10 +27,20 @@ Requires [Nim](https://nim-lang.org/) 2.x.
 ```bash
 git clone https://github.com/rolandnsharp/terminal-oscilloscope.git
 cd terminal-oscilloscope
+```
+
+**Half-block version** (chunky CRT look):
+```bash
 nim c -d:release --threads:on -o:osc src/osc.nim
 ./osc
 ```
 
+**Braille version** (high-resolution dots):
+```bash
+nim c -d:release --threads:on -o:osc_braille src/osc_braille.nim
+./osc_braille
+```
+
 ## Controls
 
 | Key | Action |
@@ -36,7 +52,7 @@ nim c -d:release --threads:on -o:osc src/osc.nim
 
 ## Configuration
 
-Edit the constants at the top of `src/osc.nim`:
+Edit the constants at the top of `src/osc.nim` or `src/osc_braille.nim`:
 
 ```nim
 const