DO NOT MERGE: prove memory-impact no-common-platform fix in CI

Chained on top of the memory-impact fix to exercise it in real CI.

Changed components and their base-test platforms:
- const: variant-only test (test-display.esp32-s3-idf.yaml, no base test).
  --base-only cannot build it, so the fix must exclude it; it only injects
  an esp32-s3-idf platform hint.
- shelly_dimmer: base test esp8266-ard (real C++).
- daikin: base test esp8266-ard (real C++), the working third component.

Without the fix, the esp32-s3-idf hint (and const's variant counted as a
supported platform) selects esp32-s3-idf, which none of the three can build
under --base-only, yielding 0 builds and a failed memory extraction. With the
fix, const is excluded, the unbuildable hint is ignored in favor of the common
esp8266-ard platform, and shelly_dimmer + daikin generate memory impact.

esphome/components/daikin/daikin.cpp

@@ -1,3 +1,5 @@
+// DNM: do not merge. Trivial touch to mark daikin changed; this is the working
+// esp8266-ard component that should generate memory impact (see PR #16788).
 #include "daikin.h"
 #include "esphome/components/remote_base/remote_base.h"
 

esphome/components/shelly_dimmer/shelly_dimmer.cpp

@@ -1,3 +1,5 @@
+// DNM: do not merge. Trivial touch to mark shelly_dimmer changed so the
+// memory-impact CI job exercises the no-common-platform fix (see PR #16788).
 #include "esphome/core/defines.h"
 #include "esphome/core/helpers.h"
 

tests/components/const/common.yaml

@@ -0,0 +1,37 @@
+display:
+  - platform: qspi_dbi
+    model: RM690B0
+    data_rate: 80MHz
+    spi_mode: mode0
+    dimensions:
+      width: 450
+      height: 600
+      offset_width: 16
+    color_order: rgb
+    invert_colors: false
+    brightness: 255
+    cs_pin: 11
+    reset_pin: 13
+    enable_pin: 9
+
+  - platform: qspi_dbi
+    model: CUSTOM
+    id: main_lcd
+    draw_from_origin: true
+    dimensions:
+      height: 240
+      width: 536
+    transform:
+      mirror_x: true
+      swap_xy: true
+    color_order: rgb
+    brightness: 255
+    cs_pin: 6
+    reset_pin: 17
+    enable_pin: 38
+    init_sequence:
+      - [0x3A, 0x66]
+      - [0x11]
+      - delay 120ms
+      - [0x29]
+      - delay 20ms

tests/components/const/test-display.esp32-s3-idf.yaml

@@ -0,0 +1,7 @@
+# DNM proof: this is a VARIANT test (test-display.*) with no base test.*.yaml.
+# The memory-impact build runs --base-only, so const has nothing buildable and
+# must be excluded; it only contributes an esp32-s3-idf platform hint.
+packages:
+  qspi: !include ../../test_build_components/common/qspi/esp32-s3-idf.yaml
+
+<<: !include common.yaml