Remove /docs slash command (#36325)

This PR removes the `/docs` slash command.

We never fully shipped this—with it requiring explicit opt-in via a
setting—and it doesn't seem like the feature is needed in an agentic
world.

Release Notes:

- Removed the `/docs` slash command.

crates/extension_host/src/extension_host.rs

@@ -16,9 +16,9 @@ pub use extension::ExtensionManifest;
 use extension::extension_builder::{CompileExtensionOptions, ExtensionBuilder};
 use extension::{
     ExtensionContextServerProxy, ExtensionDebugAdapterProviderProxy, ExtensionEvents,
-    ExtensionGrammarProxy, ExtensionHostProxy, ExtensionIndexedDocsProviderProxy,
-    ExtensionLanguageProxy, ExtensionLanguageServerProxy, ExtensionSlashCommandProxy,
-    ExtensionSnippetProxy, ExtensionThemeProxy,
+    ExtensionGrammarProxy, ExtensionHostProxy, ExtensionLanguageProxy,
+    ExtensionLanguageServerProxy, ExtensionSlashCommandProxy, ExtensionSnippetProxy,
+    ExtensionThemeProxy,
 };
 use fs::{Fs, RemoveOptions};
 use futures::future::join_all;
@@ -1192,10 +1192,6 @@ impl ExtensionStore {
             for (command_name, _) in &extension.manifest.slash_commands {
                 self.proxy.unregister_slash_command(command_name.clone());
             }
-            for (provider_id, _) in &extension.manifest.indexed_docs_providers {
-                self.proxy
-                    .unregister_indexed_docs_provider(provider_id.clone());
-            }
         }
 
         self.wasm_extensions
@@ -1399,11 +1395,6 @@ impl ExtensionStore {
                             .register_context_server(extension.clone(), id.clone(), cx);
                     }
 
-                    for (provider_id, _provider) in &manifest.indexed_docs_providers {
-                        this.proxy
-                            .register_indexed_docs_provider(extension.clone(), provider_id.clone());
-                    }
-
                     for (debug_adapter, meta) in &manifest.debug_adapters {
                         let mut path = root_dir.clone();
                         path.push(Path::new(manifest.id.as_ref()));