feat: 移动端自动重连、颜色渲染与 ENTER 键

- 移动端: 断线自动重连(指数退避, 重连后服务端下发初始快照自动恢复屏幕)
- 服务端: 语义快照新增 segments 着色分段(命名色/256色/RGB), 移动端按段渲染颜色
- 移动端: 终端按 ANSI 16 色调色板 + RGB 渲染前景/背景/粗体/斜体/下划线
- 移动端: Keybar 新增 ENTER 按钮
- 验证: 手机实测彩色输出上屏; claude -p 经同步终端运行并返回 PONG

mobile/lib/main.dart

@@ -42,6 +42,7 @@ class _TerminalPageState extends State<TerminalPage> {
   String? _sessionId;
   bool _resumed = false;
   List<String> _lines = const [];
+  List<List<Segment>> _segments = const [];
   int _cursorX = 0;
   int _cursorY = 0;
 
@@ -59,6 +60,7 @@ class _TerminalPageState extends State<TerminalPage> {
     ('↓', '\x1b[B'),
     ('←', '\x1b[D'),
     ('→', '\x1b[C'),
+    ('ENTER', '\r'),
   ];
 
   @override
@@ -106,6 +108,7 @@ class _TerminalPageState extends State<TerminalPage> {
     if (!mounted) return;
     setState(() {
       _lines = snap.lines;
+      _segments = snap.segments;
       _cursorX = snap.cursorX;
       _cursorY = snap.cursorY;
     });
@@ -343,39 +346,102 @@ class _TerminalPageState extends State<TerminalPage> {
       height: 1.25,
       color: RttyMobileTheme.text,
     );
-    if (index != _cursorY) {
-      return SizedBox(height: _lineHeight, child: Text(line, style: mono));
-    }
-
-    // 光标行：用高亮色块标出光标位置。
-    final x = _cursorX.clamp(0, line.length);
     return SizedBox(
       height: _lineHeight,
       child: Text.rich(
         TextSpan(
           style: mono,
-          children: [
-            TextSpan(text: line.substring(0, x)),
-            if (x < line.length)
-              TextSpan(
-                text: line[x],
-                style: const TextStyle(
-                  color: RttyMobileTheme.background,
-                  backgroundColor: RttyMobileTheme.primary,
-                ),
-              )
-            else
-              const TextSpan(
-                text: ' ',
-                style: TextStyle(backgroundColor: RttyMobileTheme.primary),
-              ),
-            if (x + 1 < line.length) TextSpan(text: line.substring(x + 1)),
-          ],
+          children: _lineSpans(index),
         ),
       ),
     );
   }
 
+  /// 按着色片段生成文本 spans；光标行额外叠加高亮光标块。
+  List<TextSpan> _lineSpans(int index) {
+    final segs = (index < _segments.length && _segments[index].isNotEmpty)
+        ? _segments[index]
+        : <Segment>[Segment(text: index < _lines.length ? _lines[index] : '')];
+
+    final spans = <TextSpan>[];
+    var offset = 0;
+    var cursorPlaced = false;
+    for (final seg in segs) {
+      if (seg.text.isEmpty) continue;
+      final textLen = seg.text.length;
+
+      if (!cursorPlaced &&
+          index == _cursorY &&
+          _cursorX >= offset &&
+          _cursorX <= offset + textLen) {
+        final cut = _cursorX - offset;
+        if (cut > 0) {
+          spans.add(TextSpan(text: seg.text.substring(0, cut), style: _segStyle(seg)));
+        }
+        // 光标块：覆盖该列字符（行尾则补一个空格块）。
+        final cursorChar = cut < textLen ? seg.text[cut] : ' ';
+        spans.add(TextSpan(
+          text: cursorChar,
+          style: const TextStyle(
+            color: RttyMobileTheme.background,
+            backgroundColor: RttyMobileTheme.primary,
+            fontWeight: FontWeight.bold,
+          ),
+        ));
+        if (cut + 1 < textLen) {
+          spans.add(TextSpan(text: seg.text.substring(cut + 1), style: _segStyle(seg)));
+        }
+        cursorPlaced = true;
+      } else {
+        spans.add(TextSpan(text: seg.text, style: _segStyle(seg)));
+      }
+      offset += textLen;
+    }
+
+    // 光标位于行文本之外（例如整行被去尾空白）时，行尾追加光标块。
+    if (!cursorPlaced &&
+        index == _cursorY &&
+        _cursorX >= (index < _lines.length ? _lines[index].length : 0)) {
+      spans.add(const TextSpan(
+        text: ' ',
+        style: TextStyle(backgroundColor: RttyMobileTheme.primary),
+      ));
+    }
+    return spans;
+  }
+
+  TextStyle _segStyle(Segment seg) {
+    return TextStyle(
+      fontFamily: 'monospace',
+      fontSize: 13,
+      height: 1.25,
+      color: _colorFromCode(seg.fg) ?? RttyMobileTheme.text,
+      backgroundColor: _colorFromCode(seg.bg),
+      fontWeight: seg.bold ? FontWeight.bold : null,
+      fontStyle: seg.italic ? FontStyle.italic : null,
+      decoration: seg.underline ? TextDecoration.underline : null,
+    );
+  }
+
+  /// 把服务端的颜色编码（`null` / `n:k` / `r,g,b`）解析为 Flutter 颜色。
+  Color? _colorFromCode(String? code) {
+    if (code == null) return null;
+    if (code.startsWith('n:')) {
+      final i = int.tryParse(code.substring(2)) ?? 0;
+      return _ansiPalette[i.clamp(0, 15)];
+    }
+    final parts = code.split(',');
+    if (parts.length == 3) {
+      final r = int.tryParse(parts[0]);
+      final g = int.tryParse(parts[1]);
+      final b = int.tryParse(parts[2]);
+      if (r != null && g != null && b != null) {
+        return Color.fromARGB(255, r, g, b);
+      }
+    }
+    return null;
+  }
+
   Widget _buildKeybar(bool connected) {
     return Padding(
       padding: const EdgeInsets.fromLTRB(12, 8, 12, 0),
@@ -422,6 +488,26 @@ class _TerminalPageState extends State<TerminalPage> {
   }
 }
 
+/// 标准 ANSI 16 色调色板（移动端渲染命名色用）。
+const List<Color> _ansiPalette = <Color>[
+  Color(0xFF1E1E1E), // black
+  Color(0xFFCD3131), // red
+  Color(0xFF0DBC79), // green
+  Color(0xFFE5E510), // yellow
+  Color(0xFF2472C8), // blue
+  Color(0xFFBC3FBC), // magenta
+  Color(0xFF11A8CD), // cyan
+  Color(0xFFE5E5E5), // white
+  Color(0xFF666666), // bright black
+  Color(0xFFF14C4C), // bright red
+  Color(0xFF23D18B), // bright green
+  Color(0xFFF5F543), // bright yellow
+  Color(0xFF3B8EEA), // bright blue
+  Color(0xFFD670D6), // bright magenta
+  Color(0xFF29B8DB), // bright cyan
+  Color(0xFFFFFFFF), // bright white
+];
+
 class _KeyButton extends StatelessWidget {
   const _KeyButton({required this.label, this.onTap});