feat(size_metrics): add size metrics test apps

Add test apps for binary size tracking:
- esp_timer size_metrics app with minimal/full sdkconfig variants
- minimal_baseline app to establish the platform binary size floor

components/esp_timer/test_apps/size_metrics/CMakeLists.txt

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+# Size metrics test app for esp_timer component
+cmake_minimum_required(VERSION 3.22)
+
+list(PREPEND SDKCONFIG_DEFAULTS
+     "$ENV{IDF_PATH}/tools/test_apps/configs/sdkconfig.size_metrics"
+     "sdkconfig.defaults")
+
+# "Trim" the build. Include the minimal set of components, main, and anything it depends on.
+set(COMPONENTS main)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(size_metrics)

components/esp_timer/test_apps/size_metrics/README.md

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+| Supported Targets | ESP32 | ESP32-C6 |
+| ----------------- | ----- | -------- |

components/esp_timer/test_apps/size_metrics/main/CMakeLists.txt

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+idf_component_register(SRCS "main.c"
+                       PRIV_REQUIRES esp_timer
+                       WHOLE_ARCHIVE)

components/esp_timer/test_apps/size_metrics/main/Kconfig.projbuild

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+menu "Size Metrics Test App Configuration"
+
+    choice SIZE_METRICS_FUNCTION_SET
+        prompt "Function set to compile"
+        default SIZE_METRICS_FUNCTION_SET_MINIMAL
+        help
+            Select which set of functions to compile for size metrics comparison.
+            Minimal set includes only basic functions, full set includes all features.
+
+        config SIZE_METRICS_FUNCTION_SET_MINIMAL
+            bool "Minimal function set"
+
+        config SIZE_METRICS_FUNCTION_SET_FULL
+            bool "Full function set"
+
+    endchoice
+
+endmenu

components/esp_timer/test_apps/size_metrics/main/main.c

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+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+
+#include <stdio.h>
+
+#include "esp_timer.h"
+#include "sdkconfig.h"
+
+#if CONFIG_SIZE_METRICS_FUNCTION_SET_MINIMAL
+// Minimal function set - basic timer operations only
+static void minimal_timer_callback(void* arg)
+{
+    // Minimal callback implementation
+}
+
+static void minimal_functions(void)
+{
+    esp_timer_handle_t timer;
+    esp_timer_create_args_t timer_args = {
+        .callback = minimal_timer_callback,
+        .name = "minimal_timer"
+    };
+    esp_timer_create(&timer_args, &timer);
+    esp_timer_start_once(timer, 1000);
+    esp_timer_stop(timer);
+    esp_timer_delete(timer);
+}
+#endif // CONFIG_SIZE_METRICS_FUNCTION_SET_MINIMAL
+
+#if CONFIG_SIZE_METRICS_FUNCTION_SET_FULL
+// Full function set - all timer features
+static void full_timer_callback(void* arg)
+{
+    // Full callback implementation with more features
+}
+
+static void full_periodic_timer_callback(void* arg)
+{
+    // Periodic timer callback
+}
+
+static void full_functions(void)
+{
+    esp_timer_handle_t oneshot_timer;
+    esp_timer_handle_t periodic_timer;
+
+    // One-shot timer
+    esp_timer_create_args_t oneshot_args = {
+        .callback = full_timer_callback,
+        .name = "oneshot_timer"
+    };
+    esp_timer_create(&oneshot_args, &oneshot_timer);
+    esp_timer_start_once(oneshot_timer, 1000);
+
+    // Periodic timer
+    esp_timer_create_args_t periodic_args = {
+        .callback = full_periodic_timer_callback,
+        .name = "periodic_timer"
+    };
+    esp_timer_create(&periodic_args, &periodic_timer);
+    esp_timer_start_periodic(periodic_timer, 5000);
+
+    // Timer operations
+    esp_timer_stop(oneshot_timer);
+    esp_timer_stop(periodic_timer);
+    esp_timer_delete(oneshot_timer);
+    esp_timer_delete(periodic_timer);
+}
+#endif // CONFIG_SIZE_METRICS_FUNCTION_SET_FULL
+
+void app_main(void)
+{
+    printf("size_metrics app_main started\n");
+
+#if CONFIG_SIZE_METRICS_FUNCTION_SET_MINIMAL
+    minimal_functions();
+#endif
+
+#if CONFIG_SIZE_METRICS_FUNCTION_SET_FULL
+    full_functions();
+#endif
+}

components/esp_timer/test_apps/size_metrics/pytest_size_metrics.py

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+# SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Unlicense OR CC0-1.0
+import pytest
+from pytest_embedded_idf.dut import IdfDut
+from pytest_embedded_idf.utils import idf_parametrize
+
+
+@pytest.mark.generic
+@pytest.mark.parametrize('config', ['minimal', 'full'], indirect=True)
+@idf_parametrize('target', ['esp32', 'esp32c6'], indirect=['target'])
+def test_esp_timer_size_metrics_boots(dut: IdfDut) -> None:
+    dut.expect_exact('size_metrics app_main started', timeout=30)

components/esp_timer/test_apps/size_metrics/sdkconfig.ci.full

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+# Full configuration for size metrics
+CONFIG_SIZE_METRICS_FUNCTION_SET_MINIMAL=n
+CONFIG_SIZE_METRICS_FUNCTION_SET_FULL=y

components/esp_timer/test_apps/size_metrics/sdkconfig.ci.minimal

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+# Minimal configuration for size metrics
+CONFIG_SIZE_METRICS_FUNCTION_SET_MINIMAL=y
+CONFIG_SIZE_METRICS_FUNCTION_SET_FULL=n

components/esp_timer/test_apps/size_metrics/sdkconfig.defaults

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+# App-specific defaults for esp_timer size metrics
+CONFIG_ESP_TIMER_PROFILING=n