fix: Show parent directory in file mention chips (#1472)

## Problem

File mention chips only show the filename, making it hard to distinguish between files with the same name in different directories. Absolute file paths pasted into @ mentions aren't recognized at all.

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## Changes

1. Show parent directory prefix in file mention chip labels (e.g. components/Button.tsx)
2. Add tooltip on file chips showing the full path
3. Recognize and chipify absolute file paths in @ mention suggestions
4. Add fileExists tRPC endpoint to validate absolute paths before suggesting them

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## How did you test this?

Manually

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Author: charlesvien

apps/code/src/renderer/features/message-editor/suggestions/getSuggestions.ts

@@ -1,7 +1,12 @@
 import type { AvailableCommand } from "@agentclientprotocol/sdk";
 import { CODE_COMMANDS } from "@features/message-editor/commands";
 import { getAvailableCommandsForTask } from "@features/sessions/stores/sessionStore";
-import { fetchRepoFiles, searchFiles } from "@hooks/useRepoFiles";
+import {
+  fetchRepoFiles,
+  pathToFileItem,
+  searchFiles,
+} from "@hooks/useRepoFiles";
+import { isAbsolutePath } from "@utils/path";
 import Fuse, { type IFuseOptions } from "fuse.js";
 import { useDraftStore } from "../stores/draftStore";
 import type { CommandSuggestionItem, FileSuggestionItem } from "../types";
@@ -39,26 +44,55 @@ function searchCommands(
   return results.map((result) => result.item);
 }
 
+function parentDirLabel(dir: string, name: string): string {
+  const parent = dir.split("/").filter(Boolean).pop();
+  return parent ? `${parent}/${name}` : name;
+}
+
+function getAbsolutePathSuggestion(query: string): FileSuggestionItem | null {
+  if (!isAbsolutePath(query)) return null;
+  if (!/\.\w+$/.test(query)) return null;
+
+  const fileItem = pathToFileItem(query);
+  return {
+    id: query,
+    label: parentDirLabel(fileItem.dir, fileItem.name),
+    description: fileItem.dir || undefined,
+    filename: fileItem.name,
+    path: query,
+  };
+}
+
 export async function getFileSuggestions(
   sessionId: string,
   query: string,
 ): Promise<FileSuggestionItem[]> {
   const repoPath = useDraftStore.getState().contexts[sessionId]?.repoPath;
+  const absoluteMatch = getAbsolutePathSuggestion(query);
 
   if (!repoPath) {
-    return [];
+    return absoluteMatch ? [absoluteMatch] : [];
   }
 
   const { files, fzf } = await fetchRepoFiles(repoPath);
   const matched = searchFiles(fzf, files, query);
 
-  return matched.map((file) => ({
+  const results: FileSuggestionItem[] = matched.map((file) => ({
     id: file.path,
-    label: file.name,
+    label: parentDirLabel(file.dir, file.name),
     description: file.dir || undefined,
     filename: file.name,
     path: file.path,
   }));
+
+  if (
+    absoluteMatch &&
+    !results.some((r) => `${repoPath}/${r.id}` === absoluteMatch.id)
+  ) {
+    results.unshift(absoluteMatch);
+  }
+
+  return results;
 }
 
 export function getCommandSuggestions(

apps/code/src/renderer/features/message-editor/tiptap/MentionChipView.tsx

@@ -35,8 +35,9 @@ function DefaultChip({
 
   const isCommand = type === "command";
   const prefix = isCommand ? "/" : "@";
+  const isFile = type === "file";
 
-  return (
+  const chip = (
     <span
       className={`${isCommand ? "cli-slash-command" : "cli-file-mention"} ${chipClass}`}
       contentEditable={false}
@@ -45,6 +46,12 @@ function DefaultChip({
       {label}
     </span>
   );
+
+  if (isFile) {
+    return <Tooltip content={id}>{chip}</Tooltip>;
+  }
+
+  return chip;
 }
 
 function PastedTextChip({

apps/code/src/renderer/features/sessions/components/session-update/parseFileMentions.tsx

@@ -91,12 +91,15 @@ export function parseMentionTags(content: string): ReactNode[] {
 
     if (match[1]) {
       const filePath = match[1];
-      const fileName = filePath.split("/").pop() ?? filePath;
+      const segments = filePath.split("/").filter(Boolean);
+      const fileName = segments.pop() ?? filePath;
+      const parentDir = segments.pop();
+      const label = parentDir ? `${parentDir}/${fileName}` : fileName;
       parts.push(
         <MentionChip
           key={`file-${matchIndex}`}
           icon={<File size={12} />}
-          label={fileName}
+          label={label}
         />,
       );
     } else if (match[2]) {