test(tui): isolate full-suite approval and policy fixtures

Use the existing approval timeout override guard when testing heartbeat ordering, pass an explicit managed-policy environment snapshot, clear output-limit overrides in the uncatalogued route test, and give the operator proxy success path a scheduling watchdog instead of a two-second bound.

The exact hermetic workspace libtest gate passed twice with 13456 TUI tests and zero failures. CI nextest passed 16753 selected tests; formatting and CI-policy Clippy passed. PDF failure during diagnosis coincided with exhausted /tmp inodes and passed after cleanup without a code change.

Refs #6665

crates/tui/src/mcp/http_client.rs

@@ -549,7 +549,17 @@ mod tests {
             listener,
             "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Length: 2\r\n\r\nok".to_string(),
         ));
-        let configured = client(url, false);
+        // This path proves proxy routing, not a two-second scheduling bound.
+        let configured = McpHttpClient::new(
+            url,
+            false,
+            false,
+            false,
+            None,
+            Duration::from_secs(5),
+            Duration::from_secs(10),
+        )
+        .unwrap();
         assert_eq!(
             configured
                 .send(configured.get(url))

crates/tui/src/plugins/tests.rs

@@ -1892,7 +1892,6 @@ fn malformed_managed_policy_fails_closed() {
 
 #[test]
 fn managed_policy_path_env_override_is_honored() {
-    let _lock = crate::test_support::lock_test_env();
     let tmp = tempfile::tempdir().unwrap();
     let config = config(tmp.path());
     write_plugin(&config, "");
@@ -1904,8 +1903,13 @@ fn managed_policy_path_env_override_is_honored() {
         "the default sibling must stay absent so the override is proven"
     );
 
-    let _guard = crate::test_support::EnvVarGuard::set(MANAGED_POLICY_PATH_ENV, &custom);
-    let mut registry = discover_with_config(&config);
+    let environment = super::context::HostEnvironment::from_entries([(
+        std::ffi::OsString::from(MANAGED_POLICY_PATH_ENV),
+        custom.as_os_str().to_os_string(),
+    )]);
+    let context =
+        super::context::PluginDiscoveryContext::from_config_and_environment(&config, environment);
+    let mut registry = super::discovery::discover_with_context(&config, context);
     assert_eq!(
         registry.managed_policy_path(),
         Some(custom.as_path()),

crates/tui/src/route_budget.rs

@@ -528,6 +528,9 @@ mod tests {
     /// conservative compatibility ceiling, with an attributable source.
     #[test]
     fn uncatalogued_remote_model_keeps_a_conservative_ceiling() {
+        let _lock = crate::test_support::lock_test_env();
+        let _canonical = crate::test_support::EnvVarGuard::remove("CODEWHALE_MAX_OUTPUT_TOKENS");
+        let _legacy = crate::test_support::EnvVarGuard::remove("DEEPSEEK_MAX_OUTPUT_TOKENS");
         let source = output_ceiling_source(ApiProvider::Openai, "totally-unknown-alias-v9");
         assert_eq!(
             source,

crates/tui/src/runtime_threads/tests.rs

@@ -13996,6 +13996,9 @@ async fn terminal_turn_cancels_pending_dynamic_tool_exactly_once() -> Result<()>
 /// reads as a live claim that the (already answered) call is still waiting.
 #[tokio::test]
 async fn approval_wait_heartbeat_is_never_sequenced_after_the_decision() -> Result<()> {
+    // The timeout test changes a process-wide override to 25 ms. This case
+    // checks heartbeat ordering while a decision is still pending.
+    let _timeout_guard = test_approval_timeout_ms(0);
     let manager = test_manager(test_runtime_dir())?;
     let thread = manager
         .create_thread(CreateThreadRequest::default())