add command_type to help (#14165)

# Description

This PR adds an indicator when listing subcommands. That indicator tells
whether the command is a plugin, alias, or custom_command.

![image](https://github.com/user-attachments/assets/02889f8a-17b4-4678-bb44-3a487b3d1066)

I changed some of the API to make this work a little easier, namely
`get_signatures()` is now `get_signatures_and_declids()`. It was used in
only one other place (run-external), so I thought it was fine to change
it.

There is a long-standing issue with aliases where they reference the
command name instead of the alias name. This PR doesn't fix that bug.
Example.
```nushell
❯ alias "str fill" = str wrap
```
```nushell
❯ str
... other stuff
Subcommands:

  str wrap (alias) - Alias for `str wrap`
  str wrap (plugin) - Wrap text passed into pipeline.

```


# User-Facing Changes
Slightly different output of subcommands.

crates/nu-command/src/system/run_external.rs

@@ -449,8 +449,8 @@ pub fn command_not_found(
     }
 
     // Try to match the name with the search terms of existing commands.
-    let signatures = engine_state.get_signatures(false);
-    if let Some(sig) = signatures.iter().find(|sig| {
+    let signatures = engine_state.get_signatures_and_declids(false);
+    if let Some((sig, _)) = signatures.iter().find(|(sig, _)| {
         sig.search_terms
             .iter()
             .any(|term| term.to_folded_case() == name.to_folded_case())
@@ -463,7 +463,7 @@ pub fn command_not_found(
     }
 
     // Try a fuzzy search on the names of all existing commands.
-    if let Some(cmd) = did_you_mean(signatures.iter().map(|sig| &sig.name), name) {
+    if let Some(cmd) = did_you_mean(signatures.iter().map(|(sig, _)| &sig.name), name) {
         // The user is invoking an external command with the same name as a
         // built-in command. Remind them of this.
         if cmd == name {

crates/nu-engine/src/documentation.rs

@@ -2,6 +2,7 @@ use crate::eval_call;
 use nu_protocol::{
     ast::{Argument, Call, Expr, Expression, RecordItem},
     debugger::WithoutDebug,
+    engine::CommandType,
     engine::{Command, EngineState, Stack, UNKNOWN_SPAN_ID},
     record, Category, Config, Example, IntoPipelineData, PipelineData, PositionalArg, Signature,
     Span, SpanId, Spanned, SyntaxShape, Type, Value,
@@ -112,16 +113,29 @@ fn get_documentation(
     //   - https://github.com/nushell/nushell/issues/11447
     //   - https://github.com/nushell/nushell/issues/11625
     let mut subcommands = vec![];
-    let signatures = engine_state.get_signatures(true);
-    for sig in signatures {
+    let signatures = engine_state.get_signatures_and_declids(true);
+    for (sig, decl_id) in signatures {
+        let command_type = engine_state.get_decl(decl_id).command_type();
+
         // Don't display removed/deprecated commands in the Subcommands list
         if sig.name.starts_with(&format!("{cmd_name} "))
             && !matches!(sig.category, Category::Removed)
         {
-            subcommands.push(format!(
-                "  {help_subcolor_one}{}{RESET} - {}",
-                sig.name, sig.description
-            ));
+            // If it's a plugin, alias, or custom command, display that information in the help
+            if command_type == CommandType::Plugin
+                || command_type == CommandType::Alias
+                || command_type == CommandType::Custom
+            {
+                subcommands.push(format!(
+                    "  {help_subcolor_one}{} {help_section_name}({}){RESET} - {}",
+                    sig.name, command_type, sig.description
+                ));
+            } else {
+                subcommands.push(format!(
+                    "  {help_subcolor_one}{}{RESET} - {}",
+                    sig.name, sig.description
+                ));
+            }
         }
     }
 

crates/nu-protocol/src/engine/engine_state.rs

@@ -820,14 +820,14 @@ impl EngineState {
         }
     }
 
-    /// Get signatures of all commands within scope.
-    pub fn get_signatures(&self, include_hidden: bool) -> Vec<Signature> {
+    /// Get signatures of all commands within scope with their decl ids.
+    pub fn get_signatures_and_declids(&self, include_hidden: bool) -> Vec<(Signature, DeclId)> {
         self.get_decls_sorted(include_hidden)
             .into_iter()
             .map(|(_, id)| {
                 let decl = self.get_decl(id);
 
-                self.get_signature(decl).update_from_command(decl)
+                (self.get_signature(decl).update_from_command(decl), id)
             })
             .collect()
     }