build(win-release): stop embedding Sapling params/asmap in the Lite exe

The Windows release embeds its resources into the exe through a
generated INCBIN header. The Lite build got the same param and asmap
entries as the full node, so ObsidianDragonLite.exe carried
sapling-spend.params, sapling-output.params and asmap.dat (about 53 MB)
that it never reads: the SDXL backend embeds its own copy of the params,
and Lite already skips extracting full-node-only resources.

build_release_win now writes the param and asmap INCBINs only for the
full node (should_bundle_full_node_assets). Lite gets null/zero stubs
for those three symbols and still embeds images, themes and xmrig. Two
fixes make that safe:
- getEmbeddedResource() stopped at the first table entry with null data,
  so with the params stubbed out the Lite lookup ended before xmrig:
  mining would report itself available but never find the embedded
  binary. It now walks to the end of the table and skips null payloads.
  This also fixes a full-node build without asmap, whose lookup ended at
  the null asmap entry and hid the daemon and xmrig entries.
- full and Lite builds share build/windows. When the full-node build
  cannot find the params, the generated header is now deleted, so a Lite
  header left behind by an earlier Lite build is not compiled into it
  (the node would then never start, because the startup job would take
  the embedded-extraction path and never copy the loose params).

Measured on release builds:
- ObsidianDragonLite.exe: 159,788,544 -> 106,120,192 bytes (-53.7 MB, of
  which about 0.28 MB is the ImGui demo stubs);
- the Lite header has no param or asmap INCBINs and the resource object
  holds only the xmrig payload; a sample of sapling-spend.params occurs
  once in the exe instead of twice (the remaining copy is the
  backend's);
- the full-node header is byte-identical to before.

Not verifiable here (Windows runtime): the Lite exe starting without
embedded params, and mining through the embedded xmrig. Lite installs
from older versions may still hold about 53 MB of extracted params and
asmap in %APPDATA%\ObsidianDragonLite\dragonx; nothing deletes them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/resources/embedded_resources.cpp

@@ -89,8 +89,8 @@ bool hasEmbeddedResources()
 const EmbeddedResource* getEmbeddedResource(const std::string& name)
 {
     // Search static resource table (params, daemon binaries, etc.)
-    for (const auto* res = s_resources; res->data != nullptr; ++res) {
-        if (name == res->filename) {
+    for (const auto* res = s_resources; res->filename != nullptr; ++res) {
+        if (res->data && res->size && name == res->filename) {
             return res;
         }
     }