fix: restore documentation build with tool_versions stardoc target

Add bzl_library for tool_versions.bzl to enable stardoc documentation generation.
This resolves the missing dependency for the documentation build that references
the canonical toolchain versions file.

Author: avrabe

docs/BUILD.bazel

@@ -23,6 +23,31 @@ wit_docs_collection(
 # Auto-generated API reference for all rules_wasm_component rule files
 # All outputs include Astro frontmatter for docs-site integration
 
+# ----------------------------------------------------------------------------
+# Toolchain Configuration (Tool Versions)
+# ----------------------------------------------------------------------------
+
+stardoc(
+    name = "tool_versions_stardoc_raw",
+    out = "tool_versions_raw.md",
+    input = "//toolchains:tool_versions.bzl",
+    deps = ["//toolchains:tool_versions"],
+)
+
+genrule(
+    name = "tool_versions_stardoc",
+    srcs = [":tool_versions_stardoc_raw"],
+    outs = ["tool_versions.md"],
+    cmd = """
+        echo '---' > $@
+        echo 'title: Toolchain Versions API' >> $@
+        echo 'description: Canonical versions and compatibility information for all WebAssembly ecosystem tools' >> $@
+        echo '---' >> $@
+        echo '' >> $@
+        cat $(SRCS) >> $@
+    """,
+)
+
 # ----------------------------------------------------------------------------
 # Example Rules (Tutorial/Demo)
 # ----------------------------------------------------------------------------

toolchains/BUILD.bazel

@@ -77,11 +77,19 @@ toolchain_type(
     visibility = ["//visibility:public"],
 )
 
+# Bzl library for tool versions (single source of truth)
+bzl_library(
+    name = "tool_versions",
+    srcs = ["tool_versions.bzl"],
+    visibility = ["//visibility:public"],
+)
+
 # Bzl library for toolchain implementation
 bzl_library(
     name = "wasm_toolchain",
     srcs = ["wasm_toolchain.bzl"],
     visibility = ["//visibility:public"],
+    deps = [":tool_versions"],
 )
 
 # Bzl library for wkg toolchain implementation