🤖 fix: expand tilde in plan file paths for editor deep links (#1090)

## Problem

When clicking the Edit button on a plan (Electron app, local worktree),
VSCode opens an empty file in the current working directory instead of
the actual plan file.

**Root cause:** Plan file paths contain tilde prefix
(`~/.mux/plans/...`). The backend `editorService` uses `shellQuote()`
which wraps paths in single quotes. In bash, tilde expansion doesn't
happen inside single quotes, so VSCode receives the literal `~/.mux/...`
and interprets it as a relative path.

## Solution

`readPlanFile` now uses `runtime.resolvePath()` to return absolute
paths. This works for both local (expands via `os.homedir()`) and SSH
(resolves remotely).

## Testing

- Updated integration test to assert returned paths are absolute (no
tilde)
- Manually verified Edit button works on local worktrees
- SSH workspaces continue to work (resolvePath handles remote expansion)

_Generated with mux_

Author: ethanndickson

src/node/utils/runtime/helpers.ts

@@ -145,10 +145,14 @@ export async function readPlanFile(
   const planPath = getPlanFilePath(workspaceName, projectName);
   const legacyPath = getLegacyPlanFilePath(workspaceId);
 
+  // Resolve tilde to absolute path for client use (editor deep links, etc.)
+  // For local runtimes this expands ~ to /home/user; for SSH it resolves remotely
+  const resolvedPath = await runtime.resolvePath(planPath);
+
   // Try new path first
   try {
     const content = await readFileString(runtime, planPath);
-    return { content, exists: true, path: planPath };
+    return { content, exists: true, path: resolvedPath };
   } catch {
     // Fall back to legacy path
     try {
@@ -163,10 +167,10 @@ export async function readPlanFile(
       } catch {
         // Migration failed, but we have the content
       }
-      return { content, exists: true, path: planPath };
+      return { content, exists: true, path: resolvedPath };
     } catch {
       // File doesn't exist at either location
-      return { content: "", exists: false, path: planPath };
+      return { content: "", exists: false, path: resolvedPath };
     }
   }
 }

tests/ipc/planCommands.test.ts

@@ -97,7 +97,9 @@ describeIntegration("Plan Commands Integration", () => {
         expect(result.success).toBe(true);
         if (result.success) {
           expect(result.data.content).toBe(planContent);
-          expect(result.data.path).toBe(planPath);
+          // Path should be expanded (no tilde) so it works with editor deep links
+          expect(result.data.path).toBe(expandedPlanPath);
+          expect(result.data.path).not.toContain("~");
         }
       } finally {
         await env.orpc.workspace.remove({ workspaceId });