Fix gain display precision, reorder README demos

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

README.md

@@ -2,14 +2,14 @@
 
 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)
 
+## Half-block renderer
+
+![demo](demo.gif)
+
 ## Features
 
 - **CRT boot/shutdown animations** — phosphor ramp, beam sweep, vertical collapse, dot fade

src/osc.nim

@@ -1,7 +1,7 @@
 ## Terminal oscilloscope with CRT phosphor physics.
 ## Zero dependencies beyond Nim stdlib + libav (dlopen at runtime).
 
-import os
+import os, strutils
 import posix/termios as ptermios
 from posix import read
 import osc/canvas/[term, effects]
@@ -135,7 +135,7 @@ proc main() =
     c.renderTrace(scope)
 
     let hud = " " & (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
-              " G:" & $scope.gain & " "
+              " G:" & scope.gain.formatFloat(ffDecimal, 1) & " "
     let help = " m:mode +/-:gain [/]:time q:quit "
     c.flush([(1, 0, tNormal, hud),
              (w - help.len - 1, h - 1, tDim, help)])

src/osc_braille.nim

@@ -1,6 +1,6 @@
 ## Terminal oscilloscope — braille dot rendering (4× resolution).
 
-import os
+import os, strutils
 import posix/termios as ptermios
 from posix import read
 import osc/canvas/[braille, term, effects]
@@ -129,7 +129,7 @@ proc main() =
     c.renderTrace(scope)
 
     let hud = " " & (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
-              " G:" & $scope.gain & " "
+              " G:" & scope.gain.formatFloat(ffDecimal, 1) & " "
     let help = " m:mode +/-:gain [/]:time q:quit "
     c.flush([(1, 0, tNormal, hud),
              (w - help.len - 1, h - 1, tDim, help)])