Fix auto-venv compatibility with nushell 0.108

- default-hooks: don't wrap existing hooks list in another list;
  this produced an invalid nested type that broke hook evaluation
  and downstream tab completion

- on_enter: remove transient cd operations that triggered spurious
  hook evaluations; overlay use now resolves via NU_LIB_DIRS instead
  of runtime PWD (which nushell 0.108 no longer supports for
  dynamically evaluated code)

- on_enter: guard against missing trigger file

- on_exit: guard overlay hide against inactive overlay

- venv_helpers: filter overlay list to active overlays only
  (overlay list now includes inactive entries in 0.108)

- path_extensions: return null instead of [] on no match to prevent
  type errors in downstream path join calls; return deepest ancestor
  match rather than shallowest

Author: hyiltiz

modules/virtual_environments/auto-venv/auto-venv.nu

@@ -20,7 +20,7 @@ export-env {
 
 def default-hooks [] {
     (if ($env.config.hooks.env_change.PWD != null) {
-        [$env.config.hooks.env_change.PWD]
+        $env.config.hooks.env_change.PWD
     }
     else {
         []
@@ -33,24 +33,22 @@ def build-hooks [] {
 
     let on_enter = '
         let _env = $env
-        let pwd  = $_env.PWD
 
         let trigger = (path_extensions path find-sub . __trigger__ --type ["symlink", "file"])
+        if ($trigger | is-empty) { return }
 
-        cd ($trigger | path dirname)
         overlay use __trigger__ as __auto_venv
 
-        cd ($pwd)
-
         auto-venv-on-enter $_env
 
         hide _env
-        hide pwd
         hide trigger
     '
 
     let on_exit = '
-        overlay hide __auto_venv --keep-env [PWD]
+        if (venv_helpers venv-is-active) {
+            overlay hide __auto_venv --keep-env [PWD]
+        }
     '
 
     let on_enter = ($on_enter | str replace -a '__trigger__' $trigger)

modules/virtual_environments/auto-venv/path_extensions.nu

@@ -54,6 +54,6 @@ export def "path find-sub" [
     );
 
     if ($paths != null) and ($paths | length) > 0 {
-        [ ($paths | first), $subfolder ] | path join
-    } else {[]}
+        [ ($paths | last), $subfolder ] | path join
+    } else { null }
 }

modules/virtual_environments/auto-venv/venv_helpers.nu

@@ -20,7 +20,7 @@ def get-env [
 }
 
 export def venv-is-active [] {
-    '__auto_venv' in (overlay list)
+    '__auto_venv' in (overlay list | where active | get name)
 }
 
 # Creates a virtual environment under the current directory