Revert "Load Profile state from Thread and tie visibility to the thread's model" (#30413)

This reverts commit 3615d6d96c.

Ultimately, we want to restore the ability to store a profile
per-thread, but for now reverting this fixes a fairly disruptive bug.

Release Notes:

- Fixed a bug causing the agent to use the wrong profile in some cases.

crates/agent/src/thread.rs

@@ -5,7 +5,7 @@ use std::sync::Arc;
 use std::time::Instant;
 
 use anyhow::{Result, anyhow};
-use assistant_settings::{AgentProfileId, AssistantSettings, CompletionMode};
+use assistant_settings::{AssistantSettings, CompletionMode};
 use assistant_tool::{ActionLog, AnyToolCard, Tool, ToolWorkingSet};
 use chrono::{DateTime, Utc};
 use collections::HashMap;
@@ -359,7 +359,6 @@ pub struct Thread {
     >,
     remaining_turns: u32,
     configured_model: Option<ConfiguredModel>,
-    configured_profile_id: Option<AgentProfileId>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -380,8 +379,6 @@ impl Thread {
     ) -> Self {
         let (detailed_summary_tx, detailed_summary_rx) = postage::watch::channel();
         let configured_model = LanguageModelRegistry::read_global(cx).default_model();
-        let assistant_settings = AssistantSettings::get_global(cx);
-        let configured_profile_id = assistant_settings.default_profile.clone();
 
         Self {
             id: ThreadId::new(),
@@ -424,7 +421,6 @@ impl Thread {
             request_callback: None,
             remaining_turns: u32::MAX,
             configured_model,
-            configured_profile_id: Some(configured_profile_id),
         }
     }
 
@@ -472,8 +468,6 @@ impl Thread {
             .completion_mode
             .unwrap_or_else(|| AssistantSettings::get_global(cx).preferred_completion_mode);
 
-        let configured_profile_id = serialized.profile.clone();
-
         Self {
             id,
             updated_at: serialized.updated_at,
@@ -547,7 +541,6 @@ impl Thread {
             request_callback: None,
             remaining_turns: u32::MAX,
             configured_model,
-            configured_profile_id,
         }
     }
 
@@ -603,19 +596,6 @@ impl Thread {
         cx.notify();
     }
 
-    pub fn configured_profile_id(&self) -> Option<AgentProfileId> {
-        self.configured_profile_id.clone()
-    }
-
-    pub fn set_configured_profile_id(
-        &mut self,
-        id: Option<AgentProfileId>,
-        cx: &mut Context<Self>,
-    ) {
-        self.configured_profile_id = id;
-        cx.notify();
-    }
-
     pub const DEFAULT_SUMMARY: SharedString = SharedString::new_static("New Thread");
 
     pub fn summary_or_default(&self) -> SharedString {
@@ -1120,7 +1100,6 @@ impl Thread {
                         provider: model.provider.id().0.to_string(),
                         model: model.model.id().0.to_string(),
                     }),
-                profile: this.configured_profile_id.clone(),
                 completion_mode: Some(this.completion_mode),
             })
         })