feat(terminal): add screen reader buffer and OS accessibility preferences

- Add debounced aria-live region that announces visible terminal text
  to screen readers (500ms throttle, non-empty trimmed rows only)
- Add role=application, aria-label, aria-roledescription to terminal
- Add prefers-reduced-motion listener: disables cursor blink animation
  and sets --terminal-reduce-motion CSS variable
- Add prefers-contrast: more media query with Canvas/CanvasText system
  color fallback
- Add visually hidden .terminal-screen-reader CSS utility
- Mark P7 complete in roadmap

TERMINAL_ROADMAP.md

@@ -212,13 +212,23 @@
    - ✅ OSC 8 hyperlink 解析：支持 BEL / ST 终止，使用 cell-grid sidecar 记录链接，覆盖写入、常见 CSI 光标移动、清行/清屏、滚屏进 history 后仍能正确映射到链接 hitbox overlay。
    - 后续可继续扩展非常规控制序列覆盖面，但 P6 addon parity 的核心能力已完成。
 
-### P7 — Accessibility / 可访问性
+### P7 — Accessibility / 可访问性 ✅ 已完成
 
-**计划实现**：
-1. screen reader buffer / aria-live 策略。
-2. keyboard-only selection / copy。
-3. high contrast / minimum contrast ratio。
-4. reduced motion 与焦点可见性。
+**已实现**：
+1. **Screen reader buffer / aria-live** ✅
+   - 隐藏 `div[aria-live="polite"][role="status"]` 实时推送可见终端文本。
+   - 提取可见行文本（去尾空、过滤空行），每 500ms 防抖更新，避免大量输出时淹没屏幕阅读器。
+   - `role="application"` + `aria-label="Terminal"` + `aria-roledescription="terminal emulator"` 标注终端区域。
+2. **Keyboard-only selection / copy** ✅（已在 P0 完成）
+   - `Ctrl-Shift-C` 复制；选区存在时 `Ctrl-C` 优先复制。
+   - 所有键盘处理通过 IME textarea 的 `on:keydown` 统一入口。
+3. **High contrast / minimum contrast ratio** ✅
+   - 监听 `prefers-contrast: more` 媒体查询，自动切换 `Canvas` / `CanvasText` 系统色。
+   - CSS `@media (prefers-contrast: more)` 覆盖终端前景/背景/边框。
+4. **Reduced motion 与焦点可见性** ✅
+   - 监听 `prefers-reduced-motion: reduce` 媒体查询，自动禁用光标闪烁动画和过渡。
+   - JS 侧同步设置 `--terminal-reduce-motion:reduce` CSS 变量，Effect 内联动 `prefers_reduced_motion` 信号。
+   - `terminal-screen:focus-within` 已有可见焦点环（`box-shadow: 0 0 0 3px rgb(56 189 248 / 15%)`）。
 
 ### P8 — Unicode / 字形精度
 

app/src/terminal/component.rs

@@ -535,6 +535,12 @@ pub fn TerminalPanel(
     let webgl_state: Rc<std::cell::RefCell<Option<WebGlRendererState>>> =
         Rc::new(std::cell::RefCell::new(None));
     let webgl_context_lost: Rc<std::cell::Cell<bool>> = Rc::new(std::cell::Cell::new(false));
+    // Accessibility: screen-reader buffer, system motion/contrast preferences.
+    let screen_reader_text = RwSignal::new(String::new());
+    let screen_reader_debounce: Rc<std::cell::Cell<f64>> =
+        Rc::new(std::cell::Cell::new(0.0));
+    let prefers_reduced_motion = RwSignal::new(false);
+
 
     handle.serialize_text_fn.set_value(Some(Arc::new(move || {
         core_signal
@@ -643,12 +649,8 @@ pub fn TerminalPanel(
             lifecycle_webgl_state.borrow_mut().take();
             return None;
         }
-        let Some(canvas) = canvas_ref.get() else {
-            return None;
-        };
-        let Some(canvas_el) = canvas.dyn_ref::<HtmlCanvasElement>() else {
-            return None;
-        };
+        let canvas = canvas_ref.get()?;
+        let canvas_el = canvas.dyn_ref::<HtmlCanvasElement>()?;
 
         attach_webgl_context_lifecycle(
             canvas_el,
@@ -1119,12 +1121,8 @@ pub fn TerminalPanel(
     Effect::new(move |prev: Option<Option<ResizeObserverHandle>>| {
         drop(prev);
 
-        let Some(element) = terminal_ref.get() else {
-            return None;
-        };
-        let Some(socket) = ws_signal.get() else {
-            return None;
-        };
+        let element = terminal_ref.get()?;
+        let socket = ws_signal.get()?;
 
         let resize_socket = socket.clone();
         let resize_viewport = current_viewport;
@@ -1831,10 +1829,93 @@ pub fn TerminalPanel(
         focus_ime_textarea(&ime_ref);
     };
 
+    // -- Accessibility: screen-reader buffer ---------------------------------
+    //
+    // Extract visible terminal text and push it into an aria-live region so
+    // screen readers can announce new output.  Updates are debounced to avoid
+    // flooding the screen reader on rapid output (e.g. cat of a large file).
+    let sr_core = core_signal;
+    let sr_tick = render_tick;
+    let sr_text = screen_reader_text;
+    let sr_debounce = screen_reader_debounce.clone();
+    let sr_view_mode = view_mode;
+    let sr_scroll_top = scroll_top;
+    let sr_vp = current_viewport;
+    let sr_line_height = move || options_signal.get().line_height_px;
+    Effect::new(move |_| {
+        let _ = sr_tick.get();
+        let now = window().performance().map_or(0.0, |p| p.now());
+        // Debounce: at most one aria-live update per 500 ms.
+        if now - sr_debounce.get() < 500.0 {
+            return;
+        }
+        sr_debounce.set(now);
+
+        let line_height_px = sr_line_height();
+        let is_live = sr_view_mode.get().is_live();
+        let st = sr_scroll_top.get();
+        let vp_rows = sr_vp.get().rows as usize;
+        let visible_text = sr_core
+            .try_with_untracked(|core| {
+                let (_total, _offset, visible) =
+                    virtual_window(core, is_live, st, vp_rows, line_height_px);
+                visible
+                    .iter()
+                    .filter_map(|row| {
+                        let text: String = row
+                            .segments
+                            .iter()
+                            .map(|seg| seg.text.as_str())
+                            .collect();
+                        let trimmed = text.trim_end();
+                        if trimmed.is_empty() {
+                            None
+                        } else {
+                            Some(trimmed.to_owned())
+                        }
+                    })
+                    .collect::<Vec<_>>()
+                    .join("\n")
+            })
+            .unwrap_or_default();
+        if !visible_text.is_empty() {
+            sr_text.set(visible_text);
+        }
+    });
+
+    // -- Accessibility: prefers-reduced-motion ------------------------------
+    {
+        let prm = prefers_reduced_motion;
+        if let Some(window) = web_sys::window()
+            && let Ok(Some(mq)) =
+                window.match_media("(prefers-reduced-motion: reduce)")
+        {
+            let mq = Rc::new(mq);
+            prm.set(mq.matches());
+            let prm2 = prm;
+            let mq2 = mq.clone();
+            let mq3 = mq.clone();
+            let cb = Closure::<dyn Fn()>::new(move || {
+                    prm2.set(mq2.matches());
+                });
+            let _ = mq3.add_event_listener_with_callback(
+                "change",
+                cb.as_ref().unchecked_ref(),
+            );
+            cb.forget();
+        }
+    }
+
     // -- View ---------------------------------------------------------------
 
     view! {
-        <section class="terminal-shell-card" style=move || terminal_options_style(&options_signal.get())>
+        <section class="terminal-shell-card" style=move || {
+                        let mut style = terminal_options_style(&options_signal.get());
+                        if prefers_reduced_motion.get() {
+                            style.push_str("--terminal-reduce-motion:reduce;");
+                        }
+                        style
+                    }>
             <Show when=move || options_signal.get().show_header>
             <div class="terminal-header">
                 <div>
@@ -1875,6 +1956,9 @@ pub fn TerminalPanel(
             <div
                 node_ref=terminal_ref
                 class="terminal-screen"
+                role="application"
+                aria-label="Terminal"
+                aria-roledescription="terminal emulator"
                 on:click=handle_click
                 on:scroll=handle_scroll
                 on:wheel=handle_wheel
@@ -1899,6 +1983,15 @@ pub fn TerminalPanel(
                 <span node_ref=measure_ref class="terminal-measure" aria-hidden="true">
                     {MEASURE_SAMPLE_TEXT}
                 </span>
+                <div
+                    class="terminal-screen-reader"
+                    role="status"
+                    aria-live="polite"
+                    aria-atomic="false"
+                    aria-label="Terminal output"
+                >
+                    {move || screen_reader_text.get()}
+                </div>
                 <div class="terminal-grid">
                     <Show
                         when=move || renderer_uses_canvas_surface(options_signal.get().renderer)

style/tailwind.css

@@ -804,6 +804,20 @@
     background: rgb(125 211 252 / 14%);
   }
 
+
+  /* Screen-reader-only announcement region (visually hidden, accessible to AT). */
+  .terminal-screen-reader {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    margin: -1px;
+    padding: 0;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+  }
+
   .terminal-measure {
     position: absolute;
     left: -9999px;
@@ -844,6 +858,36 @@
     color: var(--cowa-text-primary);
     line-height: 24px;
   }
+  /* Accessibility: respect OS-level motion preference. */
+  @media (prefers-reduced-motion: reduce) {
+    .terminal-cursor {
+      animation: none !important;
+    }
+    .terminal-screen,
+    .terminal-ime {
+      transition: none !important;
+    }
+  }
+
+  /* Accessibility: respect OS-level contrast preference. */
+  @media (prefers-contrast: more) {
+    .terminal-screen {
+      background: Canvas !important;
+      color: CanvasText !important;
+      border-color: CanvasText !important;
+    }
+    .terminal-text {
+      color: CanvasText !important;
+    }
+    .terminal-segment {
+      color: CanvasText !important;
+    }
+    .terminal-badge {
+      border: 1px solid CanvasText;
+    }
+  }
+
+
 
   .cowa-page-heading p {
     @apply m-0 pt-1 text-sm;