feat: Add Vimium-style link hints and vim keybindings infrastructure

- Add LINK_HINTS mode for Vimium-style link navigation
- Implement 'f' key to activate link hints mode
- Add visual mode support (v/V keys)
- Implement marks support (m[a-z] to set, '[a-z] to jump)
- Add tab navigation keys (gt/gT for next/previous tab)
- Add new actions:
  * SHOW_LINK_HINTS - activate link hints overlay
  * FOLLOW_LINK_HINT - follow link by hint letters
  * ENTER_VISUAL_MODE / ENTER_VISUAL_LINE_MODE
  * SET_MARK / GOTO_MARK - vim-style position bookmarks
  * NEXT_TAB / PREV_TAB - tab navigation
  * YANK - copy selected text

This brings modern browser vim plugin functionality (like Vimium)
to the terminal, making link navigation much faster than traditional
tab-through methods.

src/input_handler.cpp

@@ -23,7 +23,48 @@ public:
         result.has_count = false;
         result.count = 1;
 
-        // Handle digit input for count or 'f' command
+        // Handle multi-char commands like 'gg', 'gt', 'gT', 'm', '
+        if (!buffer.empty()) {
+            if (buffer == "g") {
+                if (ch == 't') {
+                    result.action = Action::NEXT_TAB;
+                    buffer.clear();
+                    count_buffer.clear();
+                    return result;
+                } else if (ch == 'T') {
+                    result.action = Action::PREV_TAB;
+                    buffer.clear();
+                    count_buffer.clear();
+                    return result;
+                }
+            } else if (buffer == "m") {
+                // Set mark with letter
+                if (std::isalpha(ch)) {
+                    result.action = Action::SET_MARK;
+                    result.text = std::string(1, static_cast<char>(ch));
+                    buffer.clear();
+                    count_buffer.clear();
+                    return result;
+                }
+                buffer.clear();
+                count_buffer.clear();
+                return result;
+            } else if (buffer == "'") {
+                // Jump to mark
+                if (std::isalpha(ch)) {
+                    result.action = Action::GOTO_MARK;
+                    result.text = std::string(1, static_cast<char>(ch));
+                    buffer.clear();
+                    count_buffer.clear();
+                    return result;
+                }
+                buffer.clear();
+                count_buffer.clear();
+                return result;
+            }
+        }
+
+        // Handle digit input for count
         if (std::isdigit(ch) && (ch != '0' || !count_buffer.empty())) {
             count_buffer += static_cast<char>(ch);
             return result;
@@ -116,16 +157,33 @@ public:
                 count_buffer.clear();
                 break;
             case 'f':
-                // 'f' command: follow link by number
+                // 'f' command: vimium-style link hints
-                if (result.has_count) {
+                result.action = Action::SHOW_LINK_HINTS;
-                    result.action = Action::FOLLOW_LINK_NUM;
+                mode = InputMode::LINK_HINTS;
-                    result.number = result.count;
+                buffer.clear();
-                    count_buffer.clear();
+                count_buffer.clear();
-                } else {
+                break;
-                    // Enter link follow mode, wait for number
+            case 'v':
-                    mode = InputMode::LINK;
+                // Enter visual mode
-                    buffer = "f";
+                result.action = Action::ENTER_VISUAL_MODE;
-                }
+                mode = InputMode::VISUAL;
+                count_buffer.clear();
+                break;
+            case 'V':
+                // Enter visual line mode
+                result.action = Action::ENTER_VISUAL_LINE_MODE;
+                mode = InputMode::VISUAL_LINE;
+                count_buffer.clear();
+                break;
+            case 'm':
+                // Set mark (wait for next char)
+                buffer = "m";
+                count_buffer.clear();
+                break;
+            case '\'':
+                // Jump to mark (wait for next char)
+                buffer = "'";
+                count_buffer.clear();
                 break;
             case ':':
                 mode = InputMode::COMMAND;
@@ -257,6 +315,75 @@ public:
 
         return result;
     }
+
+    InputResult process_link_hints_mode(int ch) {
+        InputResult result;
+        result.action = Action::NONE;
+
+        if (ch == 27) {
+            // ESC cancels link hints mode
+            mode = InputMode::NORMAL;
+            buffer.clear();
+            return result;
+        } else if (ch == KEY_BACKSPACE || ch == 127 || ch == 8) {
+            // Backspace removes last character
+            if (!buffer.empty()) {
+                buffer.pop_back();
+            } else {
+                mode = InputMode::NORMAL;
+            }
+            return result;
+        } else if (std::isalpha(ch)) {
+            // Add character to buffer
+            buffer += std::tolower(static_cast<char>(ch));
+
+            // Try to match link hint
+            result.action = Action::FOLLOW_LINK_HINT;
+            result.text = buffer;
+
+            // Mode will be reset by browser if link is followed
+            return result;
+        }
+
+        return result;
+    }
+
+    InputResult process_visual_mode(int ch) {
+        InputResult result;
+        result.action = Action::NONE;
+
+        if (ch == 27 || ch == 'v') {
+            // ESC or 'v' exits visual mode
+            mode = InputMode::NORMAL;
+            return result;
+        } else if (ch == 'y') {
+            // Yank (copy) selected text
+            result.action = Action::YANK;
+            mode = InputMode::NORMAL;
+            return result;
+        }
+
+        // Pass through navigation commands
+        switch (ch) {
+            case 'j':
+            case KEY_DOWN:
+                result.action = Action::SCROLL_DOWN;
+                break;
+            case 'k':
+            case KEY_UP:
+                result.action = Action::SCROLL_UP;
+                break;
+            case 'h':
+            case KEY_LEFT:
+                // In visual mode, h/l could extend selection
+                break;
+            case 'l':
+            case KEY_RIGHT:
+                break;
+        }
+
+        return result;
+    }
 };
 
 InputHandler::InputHandler() : pImpl(std::make_unique<Impl>()) {}
@@ -273,6 +400,11 @@ InputResult InputHandler::handle_key(int ch) {
             return pImpl->process_search_mode(ch);
         case InputMode::LINK:
             return pImpl->process_link_mode(ch);
+        case InputMode::LINK_HINTS:
+            return pImpl->process_link_hints_mode(ch);
+        case InputMode::VISUAL:
+        case InputMode::VISUAL_LINE:
+            return pImpl->process_visual_mode(ch);
         default:
             break;
     }

src/input_handler.h

@@ -8,7 +8,10 @@ enum class InputMode {
     NORMAL,
     COMMAND,
     SEARCH,
-    LINK
+    LINK,
+    LINK_HINTS,    // Vimium-style 'f' mode
+    VISUAL,        // Visual mode
+    VISUAL_LINE    // Visual line mode
 };
 
 enum class Action {
@@ -28,12 +31,24 @@ enum class Action {
     FOLLOW_LINK,
     GOTO_LINK,        // Jump to specific link by number
     FOLLOW_LINK_NUM,  // Follow specific link by number (f command)
+    SHOW_LINK_HINTS,  // Activate link hints mode ('f')
+    FOLLOW_LINK_HINT, // Follow link by hint letters
     GO_BACK,
     GO_FORWARD,
     OPEN_URL,
     REFRESH,
     QUIT,
-    HELP
+    HELP,
+    ENTER_VISUAL_MODE,      // Start visual mode
+    ENTER_VISUAL_LINE_MODE, // Start visual line mode
+    SET_MARK,               // Set a mark (m + letter)
+    GOTO_MARK,              // Jump to mark (' + letter)
+    YANK,                   // Copy selected text
+    NEXT_TAB,               // gt - next tab
+    PREV_TAB,               // gT - previous tab
+    NEW_TAB,                // :tabnew
+    CLOSE_TAB,              // :tabc
+    TOGGLE_MOUSE            // Toggle mouse support
 };
 
 struct InputResult {