fix(fs): observe absence before guarded recreation

packages/fs/tool-str-replace-editor/tests/tools.spec.ts

@@ -196,6 +196,35 @@ describe('tool-str-replace-editor', () => {
     expect(await readFile(sample, 'utf8')).toBe('one\nbetween\n\nthree\n')
   })
 
+  it('a failed view records absence so create can recover after external deletion', async () => {
+    const { ctx, root, owner } = await setup({}, { fsPolicy: true })
+    const sample = join(root, 'deleted.txt')
+    await writeFile(sample, 'original')
+    expect((await call(ctx, owner, { command: 'view', path: sample })).isError).toBe(false)
+    await rm(sample)
+
+    const missing = await call(ctx, owner, { command: 'view', path: sample })
+    expect(missing.isError).toBe(true)
+    expect(missing.error).toMatchObject({ info: { code: 'FS_NOT_FOUND' } })
+
+    const edit = await call(ctx, owner, {
+      command: 'str_replace',
+      path: sample,
+      old_str: 'original',
+      new_str: 'edited',
+    })
+    expect(edit.isError).toBe(true)
+    expect(edit.error).toMatchObject({ info: { code: 'FS_NOT_FOUND' } })
+
+    const created = await call(ctx, owner, {
+      command: 'create',
+      path: sample,
+      file_text: 'fresh',
+    })
+    expect(created.isError).toBe(false)
+    expect(await readFile(sample, 'utf8')).toBe('fresh')
+  })
+
   it('writes replacement text literally', async () => {
     const { ctx, root, owner } = await setup()
     const sample = join(root, 'literal.txt')