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/flexoki-light.json

@@ -48,7 +48,7 @@
     "#CE5D97",
     "#3AA99F",
     "#FFFCF0",
-    "#100F0F",
+    "#6F6E69",
     "#D14D41",
     "#879A39",
     "#D0A215",