Add Wi-Fi/TLS heap probe; limit deep+ LDF to native tests

The deep+ dependency finder broke the framework's WiFi -> Network
include on the device build; only the native test env needs it.
The probe serial command (probe <ssid>TAB<password>) measures heap
with Wi-Fi connected and one TLS connection; credentials never touch
the repo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

platformio.ini

@@ -7,7 +7,6 @@ default_envs = cardputer-adv
 [env]
 extra_scripts = pre:scripts/version.py
 test_framework = unity
-lib_ldf_mode = deep+
 
 [env:cardputer-adv]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.312/platform-espressif32.zip
@@ -25,4 +24,5 @@ test_ignore = *
 ; Host-side unit tests for pure logic (no hardware).
 [env:native]
 platform = native
+lib_ldf_mode = deep+
 build_flags = -std=gnu++17