test: align runtime fixtures across platforms

Account for Electron-as-Node when probing the current executable and update the Linux workspace registry scenario to validate the writable handle behavior shipped with remote file management.

src/agent-daemon/workspace-registry.test.ts

@@ -137,7 +137,7 @@ describe('WorkspaceRegistry', () => {
     ).rejects.toMatchObject({ code: 'workspace-not-found' })
   })
 
-  linuxIt('enforces read-only policy, caps, and symlink-root rejection', async () => {
+  linuxIt('supports writable handles while enforcing caps and symlink-root rejection', async () => {
     const root = temporaryDirectory()
     const linked = join(tmpdir(), `goodbuddy-linked-${Date.now()}`)
     symlinkSync(root, linked, 'dir')
@@ -149,16 +149,20 @@ describe('WorkspaceRegistry', () => {
       maximumControllerHandles: 1,
       inspectGit: async () => 'not-a-repository'
     })
-    await expect(
-      registry.validate(
-        {
-          remoteRootPath: root,
-          requestedAccess: 'read-write',
-          requiredCapabilities: []
-        },
-        controller
-      )
-    ).rejects.toMatchObject({ code: 'read-only' })
+    const writable = await registry.validate(
+      {
+        remoteRootPath: root,
+        requestedAccess: 'read-write',
+        requiredCapabilities: []
+      },
+      controller
+    )
+    expect(writable.handle.access).toBe('read-write')
+    await registry.close(
+      writable.handle.workspaceId,
+      writable.handle.generation,
+      controller
+    )
     await expect(
       registry.validate(
         {

src/main/agent/runtime-discovery.test.ts

@@ -75,7 +75,7 @@ describe('runtime discovery', () => {
     await expect(validation).resolves.toEqual({ valid: false })
   })
 
-  it('canonicalizes a configured ordinary file without launching it', async () => {
+  it('canonicalizes and validates a configured ordinary file first', async () => {
     process.env.PATH = ''
     process.env.Path = ''
 
@@ -90,7 +90,11 @@ describe('runtime discovery', () => {
       path: await realpath(process.execPath),
       source: 'configured'
     })
-    expect(detection.version).toBeUndefined()
+    if (process.versions.electron) {
+      expect(detection.version).toBeUndefined()
+    } else {
+      expect(detection.version).toMatch(/^\d+\.\d+\.\d+/u)
+    }
   })
 
   it('trusts a configured execution path without reading or launching it', async () => {