fix(themes): fidelity hierarchy nits + #52 residual ANSI (#67, #68)

#67 hierarchy: nord subtext dimmer than text; tokyo-night btop Night
blues; ethereal surface raise + muted darker than overlay; retro-82
surface raised; ristretto subtext distinct + btop main_bg align;
flexoki-light distinct bright-black; gruvbox overlay/subtext ladder
(no rename).

#68 residual ANSI: vantablack ansi[8]=muted; osaka-jade ansi[3]=warn.

Verified: python3 tools/check-theme-contrast.py themes/ → 24×7 all pass.

themes/tokyo-night/btop.theme

@@ -5,10 +5,10 @@
 theme[main_bg]="#1a1b26"
 
 # Main text color
-theme[main_fg]="#cfc9c2"
+theme[main_fg]="#a9b1d6"
 
 # Title color for boxes
-theme[title]="#cfc9c2"
+theme[title]="#a9b1d6"
 
 # Highlight color for keyboard shortcuts
 theme[hi_fg]="#7dcfff"
@@ -17,7 +17,7 @@ theme[hi_fg]="#7dcfff"
 theme[selected_bg]="#414868"
 
 # Foreground color of selected item in processes box
-theme[selected_fg]="#cfc9c2"
+theme[selected_fg]="#a9b1d6"
 
 # Color of inactive/disabled text
 theme[inactive_fg]="#565f89"