fix(ai): keep in-memory defaults seeded when prefs is unavailable

The defaults_initialized sentinel only makes sense when prefs is loaded.
Three unit tests use ai_client_setup, which calls ai_client_init without
loading prefs — prefs_ai_get_providers was bailing on the seeding branch
because of the prefs NULL check, leaving ai_client with zero providers
and breaking tests that expect at least one default.

Decouple the two concerns:
- Always seed openai/perplexity into the in-memory result list when the
  configured set is empty and we haven't already seeded.
- Only persist the seeded providers and write the defaults_initialized
  flag when prefs is actually available.

In production this is identical to the previous behaviour; in tests
without prefs the old "always-return-defaults" semantics is preserved
without a persistence side effect.

Also reflow ai_client.c JSON escape switch and HTTP-error ternary to
satisfy clang-format 18 (CI checks).

src/ai/ai_client.c

@@ -197,15 +197,41 @@ _json_unescape_substring(const gchar* start, const gchar* end)
     for (const gchar* in = start; in < end;) {
         if (*in == '\\' && in + 1 < end) {
             switch (in[1]) {
-            case '"':  *w++ = '"';  in += 2; break;
-            case '\\': *w++ = '\\'; in += 2; break;
-            case '/':  *w++ = '/';  in += 2; break;
-            case 'n':  *w++ = '\n'; in += 2; break;
-            case 't':  *w++ = '\t'; in += 2; break;
-            case 'r':  *w++ = '\r'; in += 2; break;
-            case 'b':  *w++ = '\b'; in += 2; break;
-            case 'f':  *w++ = '\f'; in += 2; break;
-            default:   *w++ = *in++; break;
+            case '"':
+                *w++ = '"';
+                in += 2;
+                break;
+            case '\\':
+                *w++ = '\\';
+                in += 2;
+                break;
+            case '/':
+                *w++ = '/';
+                in += 2;
+                break;
+            case 'n':
+                *w++ = '\n';
+                in += 2;
+                break;
+            case 't':
+                *w++ = '\t';
+                in += 2;
+                break;
+            case 'r':
+                *w++ = '\r';
+                in += 2;
+                break;
+            case 'b':
+                *w++ = '\b';
+                in += 2;
+                break;
+            case 'f':
+                *w++ = '\f';
+                in += 2;
+                break;
+            default:
+                *w++ = *in++;
+                break;
             }
         } else {
             *w++ = *in++;
@@ -688,9 +714,9 @@ _curl_exec_and_handle(CURL* curl, const gchar* url, struct curl_slist* headers,
     } else if (http_code >= 400) {
         auto_gchar gchar* parsed = ai_parse_error_message(response->data);
         auto_gchar gchar* error_msg = parsed
-            ? g_strdup_printf("HTTP %ld: %s", http_code, parsed)
-            : g_strdup_printf("HTTP %ld: %s", http_code,
-                              response->data && strlen(response->data) > 0 ? response->data : "Unknown error");
+                                          ? g_strdup_printf("HTTP %ld: %s", http_code, parsed)
+                                          : g_strdup_printf("HTTP %ld: %s", http_code,
+                                                            response->data && strlen(response->data) > 0 ? response->data : "Unknown error");
         log_error("Request HTTP error for '%s': %s", provider->name, error_msg);
         _aiwin_display_error(user_data, error_msg);
     } else {

src/config/preferences.c

@@ -67,7 +67,7 @@
 #define PREF_GROUP_PLUGINS       "plugins"
 #define PREF_GROUP_EXECUTABLES   "executables"
 #define PREF_GROUP_AI            "ai"
-#define PREF_GROUP_AI_PREFIX     "ai/"     /* per-provider subsection prefix: [ai/<provider>] */
+#define PREF_GROUP_AI_PREFIX     "ai/"      /* per-provider subsection prefix: [ai/<provider>] */
 #define PREF_AI_SETTING_PREFIX   "setting." /* per-provider custom setting key prefix */
 
 #define INPBLOCK_DEFAULT 1000
@@ -2045,18 +2045,25 @@ prefs_ai_get_providers(void)
     }
     prefs_free_ai_providers(configured);
 
-    /* Seed openai/perplexity once on very first init only — driven by the
-     * "defaults_initialized" sentinel so a user who removes every provider
-     * does not get them silently re-added. */
-    if (prefs && !g_key_file_get_boolean(prefs, PREF_GROUP_AI, "defaults_initialized", NULL)) {
-        if (!result) {
+    /* Seed openai/perplexity into the in-memory result on very first init
+     * only. In production the "defaults_initialized" sentinel in [ai] is what
+     * tells us we've already seeded — a user who removes every provider must
+     * not get them silently re-added on the next start. When prefs is NULL
+     * (e.g. unit tests that bring up ai_client without prefs_load) we still
+     * seed the in-memory list so behaviour matches a fresh first run, but
+     * skip the persistence write. */
+    gboolean already_seeded = prefs && g_key_file_get_boolean(prefs, PREF_GROUP_AI, "defaults_initialized", NULL);
+    if (!already_seeded && !result) {
+        if (prefs) {
             prefs_ai_set_provider("openai", "https://api.openai.com/");
             prefs_ai_set_provider("perplexity", "https://api.perplexity.ai/");
-            result = g_list_append(result, g_strdup("openai"));
-            result = g_list_append(result, g_strdup("https://api.openai.com/"));
-            result = g_list_append(result, g_strdup("perplexity"));
-            result = g_list_append(result, g_strdup("https://api.perplexity.ai/"));
         }
+        result = g_list_append(result, g_strdup("openai"));
+        result = g_list_append(result, g_strdup("https://api.openai.com/"));
+        result = g_list_append(result, g_strdup("perplexity"));
+        result = g_list_append(result, g_strdup("https://api.perplexity.ai/"));
+    }
+    if (prefs && !already_seeded) {
         g_key_file_set_boolean(prefs, PREF_GROUP_AI, "defaults_initialized", TRUE);
         _save_prefs();
     }