feat(sim): port examples/simple_room_server to variants/sim/

Mirrors the simple_repeater sim port exactly: headless (no DISPLAY_CLASS,
UITask.cpp excluded from the build), new sim_simple_room_server native env
plus build_wasm_room_server.sh, own SimFS root ./sim_data_room so its
identity storage can't collide with the companion or repeater instances on
the same page/cwd.

Verified beyond "it compiles": ran the native binary and confirmed a real
_main.id identity file gets persisted through the actual SimFS/IdentityStore
path, same as the other two sim targets.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

variants/sim/platformio.ini

@@ -138,3 +138,56 @@ build_src_filter =
   ; rather than porting GPIO stubs into variants/sim/arduino/Arduino.h for
   ; code that would never run.
   -<../examples/simple_repeater/UITask.cpp>
+
+; Headless native build of the real examples/simple_room_server app logic
+; against the same variants/sim/ interfaces -- sibling of
+; [env:sim_simple_repeater] above, same reasoning throughout (no
+; DISPLAY_CLASS, so UITask.cpp is never needed here either -- unlike
+; simple_repeater's, this one's UITask.cpp actually WOULD compile fine
+; headless (its digitalRead(PIN_USER_BTN) call is itself gated behind
+; #ifdef PIN_USER_BTN, which this env never defines), but there's still no
+; reason to compile a translation unit that's never linked in, so it's
+; excluded the same way).
+[env:sim_simple_room_server]
+platform = native
+build_type = debug
+build_flags =
+  -std=c++17
+  -g
+  -funsigned-char
+  -D SIM_PLATFORM
+  -D MESH_DEBUG=0
+  -D ENABLE_ADVERT_ON_BOOT=1
+  -D ADVERT_NAME='"Sim Room"'
+  -I variants/sim/arduino
+  -I variants/sim
+  -I variants/sim/thirdparty/crypto
+  -I variants/sim/thirdparty/cayennelpp
+  -I variants/sim/thirdparty/arduinojson
+  -I lib/ed25519
+  -I src
+  -I examples/simple_room_server
+build_src_filter =
+  -<*>
+  +<../src/Dispatcher.cpp>
+  +<../src/Identity.cpp>
+  +<../src/Mesh.cpp>
+  +<../src/Packet.cpp>
+  +<../src/Utils.cpp>
+  +<../src/helpers/AdvertDataHelpers.cpp>
+  +<../src/helpers/BaseChatMesh.cpp>
+  +<../src/helpers/ClientACL.cpp>
+  +<../src/helpers/CommonCLI.cpp>
+  +<../src/helpers/ConfigSerializer.cpp>
+  +<../src/helpers/DeviceDiag.cpp>
+  +<../src/helpers/IdentityStore.cpp>
+  +<../src/helpers/RegionMap.cpp>
+  +<../src/helpers/StaticPoolPacketManager.cpp>
+  +<../src/helpers/TransportKeyStore.cpp>
+  +<../src/helpers/TxtDataHelpers.cpp>
+  +<../lib/ed25519/*.c>
+  +<../variants/sim/*.cpp>
+  +<../variants/sim/thirdparty/crypto/*.cpp>
+  +<../variants/sim/thirdparty/cayennelpp/*.cpp>
+  +<../examples/simple_room_server/*.cpp>
+  -<../examples/simple_room_server/UITask.cpp>