feat(tool-fs): editor-facing presentation for read/write/edit

The fs tools rendered as generic cards (title = tool name, raw file content) in
an ACP editor. Give them tool-owned presentation like bash/subagent have:

- read → title "Read <path>", kind read, offset/limit as rawInput
- write → title "Write <path>", kind edit
- edit → title "Edit <path>", kind edit, a clipped old→new rawInput summary

Add a provider-neutral `locations: { path, line? }[]` to ToolCallPresentation —
the files a call reads/modifies — so a capable editor can follow along / jump to
the file (read carries its offset as the line). The ACP bridge forwards it onto
the wire `tool_call` (ResolvedCallPresentation + call() + the tool_call build in
streamSessionEventUpdate). This flips the `locations` cell in the ACP feature
matrix to supported. The SDK already carries `tool_call.locations`
(ToolCallLocation `{ path, line? }`), so no ACP types leak into dsh-tools.

presentResult is intentionally omitted: it only receives `{ content, isError }`,
not the write/edit outcome, so titling by create-vs-overwrite or replacement
count would mean parsing the model-facing text — the static title stays.

Tests: pure presentCall assertions for all three tools incl. locations and the
edit rawInput clip; a bridge test drives the REAL fs tools through ToolPresenter
and asserts locations reaches the wire tool_call (proven to fail without the
forwarding line). New withFs harness option + dsh-fs devDeps on dsh-acp.

packages/fs/tool-fs/src/read.ts

@@ -101,5 +101,20 @@ export function applyReadTool(ctx: Context): void {
       ctx.emit('fs/observed', target, info.version, exec)
       return [{ type: 'text', text: formatReadOutput(target.displayPath, outcome) }]
     },
+    // Pure display: a UI card titled by the file, `read` kind (icon), and a
+    // location so an editor can follow along to the file (and the read's offset
+    // line). `rawInput` surfaces offset/limit when the model narrowed the read.
+    presentCall(args) {
+      const detail = [
+        ...args.offset !== undefined ? [`offset ${args.offset}`] : [],
+        ...args.limit !== undefined ? [`limit ${args.limit}`] : [],
+      ].join(', ')
+      return {
+        title: `Read ${args.file_path}`,
+        kind: 'read',
+        locations: [{ path: args.file_path, ...args.offset !== undefined ? { line: args.offset } : {} }],
+        ...detail.length > 0 ? { rawInput: detail } : {},
+      }
+    },
   }))
 }