fix: README mobile layout — remove float that breaks narrow viewports

The Mobile-Optimized Web UI section used align="left" on a 280px image,
leaving only ~110px for text on 390px mobile screens. This caused
single-character-per-line text wrapping on GitHub mobile view. Changed
to stacked layout: text description above, centered image, then
comparison table below.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -68,10 +68,12 @@ Claudeman requires tmux, so Windows users need [WSL](https://learn.microsoft.com
 
 ## Mobile-Optimized Web UI
 
-<img src="docs/screenshots/mobile-keyboard-open.png" alt="Mobile — keyboard open" width="280" align="left">
-
 The most responsive Claude Code experience on any phone. Full xterm.js terminal with local echo, swipe navigation, and a touch-optimized interface designed for real remote work.
 
+<p align="center">
+  <img src="docs/screenshots/mobile-keyboard-open.png" alt="Mobile — keyboard open" width="280">
+</p>
+
 | Terminal Apps | Claudeman Mobile |
 |:--------------|:-----------------|
 | 200-300ms input lag over remote | **Local echo — instant feedback** |
@@ -82,8 +84,6 @@ The most responsive Claude Code experience on any phone. Full xterm.js terminal
 | No agent visibility | Background agents in real-time |
 | Copy-paste slash commands | One-tap `/init`, `/clear`, `/compact` buttons |
 
-<br clear="both">
-
 - **Swipe navigation** — left/right on the terminal to switch sessions (80px threshold, 300ms)
 - **Keyboard accessory bar** — `/init`, `/clear`, `/compact` quick-action buttons appear above the virtual keyboard with confirmation dialogs for destructive commands
 - **Smart keyboard handling** — toolbar and terminal shift up when keyboard opens (uses `visualViewport` API with 100px threshold for iOS address bar drift)