Tab5: fix black screen at boot, power the keyboard and WiFi; hold Ctr…

[bluenevus]

…l to talk

• Main task stack 12 KB on both boards (sdkconfig.defaults). The T-Deck had it only in its committed sdkconfig, so the Tab5 got the 3.5 KB default and app_main overflowed while bringing up the SD card, display and terminal screen (black screen, reboot loop). Speed optimization, assertions off and WARN logging moved to the shared defaults the same way; the T-Deck's sdkconfig is unchanged. Guard: main task stack >= 12 KB for both boards.
• IO expanders: after the driver's reset every pin is high-impedance, so set_dir/set_level alone never drove the keyboard's 5 V, the ESP32-C6 power or the charger. Outputs are now push-pull, with M5Stack's levels: internal antenna, USB-A 5 V off, no power-off pulse, standard (not quick) charging.
• Chat push-to-talk on the Tab5: hold Ctrl on its own (was Ctrl+Space). Another key pressed first makes it a control code; a long hold only deletes a history entry when Ctrl was alone.
• sdkconfig.tab5 regenerated from the locked components (LVGL 9.4.0, as the T-Deck).

RAM: T-Deck 116,199 bytes static (unchanged), Tab5 98,294. Not yet confirmed on a Tab5.