Shrink NimBLE footprint to prevent stack overflow

Reduce BLE stack memory usage from ~68KB to ~52KB by disabling unused NimBLE roles (peripheral, broadcaster), limiting connections to 1, and reducing buffer counts for ACL, HCI events, and ATT entries. Remove unused cloud components (esp_insights, esp_rainmaker) that require unavailable server certificates. These changes prevent stack collision with the render shed, eliminating restart flaps on the reader device.

platformio.ini

@@ -60,6 +60,48 @@ board_build.flash_mode = dio
 board_build.flash_size = 16MB
 board_build.partitions = partitions.csv
 
+; Shrink the NimBLE footprint for a 1-connection HID host moving 3-6 byte reports.
+; Field-measured: begin() costs ~52 KB with these trims vs ~68 KB with the prebuilt
+; framework defaults — and that 15 KB is the difference between the stack landing
+; above the reader's render shed floor (stable coexistence) and below it (a
+; guaranteed shed/restart flap). Rebuilds the Arduino core libs on first build
+; (slower once, cached after; needs the CMake pin in platformio.local.ini on macOS).
+custom_sdkconfig =
+  CONFIG_BT_NIMBLE_ROLE_PERIPHERAL=n
+  CONFIG_BT_NIMBLE_ROLE_BROADCASTER=n
+  CONFIG_BT_NIMBLE_MAX_CONNECTIONS=1
+  CONFIG_BT_NIMBLE_MAX_CCCDS=2
+  CONFIG_BT_NIMBLE_ATT_PREFERRED_MTU=23
+  CONFIG_BT_NIMBLE_MSYS_1_BLOCK_COUNT=6
+  CONFIG_BT_NIMBLE_MSYS_2_BLOCK_COUNT=6      ; was 24 x 320 B
+  CONFIG_BT_NIMBLE_ACL_BUF_COUNT=6           ; was 24 x 255 B
+  CONFIG_BT_NIMBLE_HCI_EVT_HI_BUF_COUNT=12   ; was 30 x 70 B; only scan bursts need many
+  ; IDF 5.5 sizes the HCI transport pools under TRANSPORT_* names; pin both spellings.
+  CONFIG_BT_NIMBLE_TRANSPORT_ACL_FROM_LL_COUNT=6
+  CONFIG_BT_NIMBLE_TRANSPORT_EVT_COUNT=12
+  CONFIG_BT_NIMBLE_ATT_MAX_PREP_ENTRIES=4    ; was 64; a HID host never does prepared writes
+  CONFIG_BT_CTRL_BLE_MAX_ACT=3               ; was 6; need conn + scan + initiate only
+  CONFIG_BT_CTRL_BLE_ADV_REPORT_FLOW_CTRL_NUM=50   ; was 100; pairing-time scan only
+  CONFIG_BT_CTRL_ADV_DUP_FILT_MAX=10               ; was 30
+  ; Keep the Arduino wrappers for the removed cloud components (below) out of
+  ; the core source list; all other bundled libraries default to enabled.
+  CONFIG_ARDUINO_SELECTIVE_COMPILATION=y
+  CONFIG_ARDUINO_SELECTIVE_RainMaker=n
+  CONFIG_ARDUINO_SELECTIVE_Insights=n
+
+; Drop unused cloud components from the core rebuild. esp_insights/rainmaker
+; require embedded server certs the lib builder can't generate
+; ("https_server.crt.S not found"); this firmware uses none of them.
+custom_component_remove =
+  espressif/esp_insights
+  espressif/esp_rainmaker
+  espressif/esp_diagnostics
+  espressif/esp_diag_data_store
+  espressif/esp_schedule
+  espressif/esp_rcp_update
+  espressif/esp_secure_cert_mgr
+  espressif/cbor
+
 extra_scripts =
   pre:scripts/build_html.py
   pre:scripts/gen_i18n.py