zx: make ZLS resolve build-graph modules in .zx files

zxls forwards .zx files to ZLS under their real .zx URI (the *content* is
transpiled to Zig, but the URI keeps the .zx extension). This patches enables .zx files in ZLS

Apply from the ZLS package root:  git apply patchs/zls.patch
                          (or)    patch -p1 < patchs/zls.patch

Generated against ZLS 0.16.0 @ 494486203c3a48927f2383aa3d5ce5fca112186d

--- a/src/DocumentStore.zig
+++ b/src/DocumentStore.zig
@@ -51,6 +51,16 @@
     },
 };
 
+// zx: zxls forwards `.zx` files to ZLS under their real `.zx` URI (zxls
+// transpiles the *content* to Zig but keeps the URI). For cross-file imports to
+// resolve, ZLS must treat `.zx` as a Zig file import just like `.zig`.
+
+/// Whether `import_string` refers to a Zig source file (`.zig` or `.zx`).
+fn isZigFileImport(import_string: []const u8) bool {
+    return std.mem.endsWith(u8, import_string, ".zig") or
+        std.mem.endsWith(u8, import_string, ".zx");
+}
+
 /// Represents a `build.zig`
 pub const BuildFile = struct {
     uri: Uri,
@@ -115,6 +125,12 @@
 
         var module_root_source_file_paths: std.ArrayList([]const u8) = .empty;
 
+        // zx: `.zx` page files are routed by the zx framework rather than reached
+        // via `@import`, so they never appear in the import graph below. As a
+        // fallback, associate any `.zx` file located under the build file's
+        // directory with the first compilation's root module.
+        var zx_fallback_root: ?[]const u8 = null;
+
         {
             const build_config = build_file.tryLockConfig(io) orelse return .unknown;
             defer build_file.unlockConfig(io);
@@ -124,6 +140,13 @@
             try module_root_source_file_paths.ensureUnusedCapacity(arena, module_paths.len);
             for (module_paths) |module_path| {
                 module_root_source_file_paths.appendAssumeCapacity(try arena.dupe(u8, module_path));
+            }
+
+            if (std.mem.endsWith(u8, uri.raw, ".zx") and build_config.compilations.len != 0) {
+                const build_dir = std.Io.Dir.path.dirname(build_file.uri.raw) orelse build_file.uri.raw;
+                if (std.mem.startsWith(u8, uri.raw, build_dir)) {
+                    zx_fallback_root = try arena.dupe(u8, build_config.compilations[0].root_module);
+                }
             }
         }
 
@@ -148,6 +171,8 @@
             }
         }
 
+        if (zx_fallback_root) |root| return .{ .yes = try allocator.dupe(u8, root) };
+
         return .no;
     }
 
@@ -516,7 +541,7 @@
                 var import_string = offsets.tokenToSlice(tree, tree.nodeMainToken(params[0]));
                 import_string = import_string[1 .. import_string.len - 1];
 
-                if (!std.mem.endsWith(u8, import_string, ".zig")) continue;
+                if (!isZigFileImport(import_string)) continue;
 
                 const import_uri = try Uri.resolveImport(allocator, uri, parsed_uri, import_string);
                 file_imports.appendAssumeCapacity(import_uri);
@@ -1984,7 +2009,7 @@
     const tracy_zone = tracy.trace(@src());
     defer tracy_zone.end();
 
-    if (std.mem.endsWith(u8, import_str, ".zig") or std.mem.endsWith(u8, import_str, ".zon")) {
+    if (isZigFileImport(import_str) or std.mem.endsWith(u8, import_str, ".zon")) {
         const parsed_uri = handle.uri.toStdUri();
         return .{ .one = try Uri.resolveImport(allocator, handle.uri, parsed_uri, import_str) };
     }