fix(web-read-card): align highlight grammars with read hints, fix fixture schema, restore running sweep

Register the full grammar set the read tool's langFromPath emits (python,
go, rust, yaml, markdown, html, and the rest) so a read card highlights the
same extensions the backend recognizes instead of returning undefined for
them. Rewrite highlightLines' terminator-line check to the explicit
last !== undefined form to keep a single branch for per-file coverage.

Add the running-state sweep animation to ReadRow, matching BashRow/ToolRow,
so a running read row shows executing feedback.

Use file_path (the real read tool schema field) in the turn 66 read fixture
sample, its presentCall branch, and the turn 64 run_code read sub-dispatches,
so the built-boot snapshot replays a production-shaped call and the details
panel shows the correct Input JSON.

Document why ReadBlock omits TerminalBlock's empty-window copy guard, and
correct the read-card-model {@link} and the turn 66 fixture comment.

packages/client/ui-conversation/src/client/contract/read-card-model.ts

@@ -23,7 +23,8 @@ import { relativizeToCwd, type ToolCallBlock } from './tool-call-model.ts'
  * scannable across many calls, while the details panel is the single-call
  * reading surface. A design constant of this UI's row geometry, not a
  * deployment choice, so it is fixed here rather than a plugin Config field. The
- * same split {@link CHAT_TERMINAL_MAX_LINES} draws for terminal output.
+ * same split [`CHAT_TERMINAL_MAX_LINES`](./terminal-card-model.ts) draws for
+ * terminal output.
  */
 export const CHAT_READ_MAX_LINES = 8
 

packages/client/ui-conversation/src/client/toolviews/read-row.module.css

@@ -15,7 +15,7 @@
 }
 
 .root {
-  position: relative;
+  position: relative; /* sweep-glare overlay anchor */
   overflow: hidden;
   display: flex;
   align-items: center;
@@ -23,6 +23,32 @@
   min-width: 0;
 }
 
+/* Running sweep glare — same pattern as BashRow/ToolRow, so a running read row
+   gives the same executing feedback a running command row does. The leading
+   read icon stays static (a read has no per-step state to animate); the sweep
+   is the row-level running signal. */
+.root[data-state='running']::after {
+  content: '';
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  left: 0;
+  width: 300px;
+  background: linear-gradient(
+    90deg,
+    transparent 0%,
+    color-mix(in srgb, var(--dsw-alias-bg-base) 60%, transparent) 55%,
+    transparent 100%
+  );
+  animation: dsh-read-row-sweep 2.6s ease-out infinite;
+  pointer-events: none;
+}
+
+@keyframes dsh-read-row-sweep {
+  0% { left: -300px; }
+  90%, 100% { left: 100%; }
+}
+
 .leading {
   flex: none;
   width: 16px;