feat: add phase 6 js_library and ts_library bootstrap

internal/js_library.bzl

@@ -0,0 +1,40 @@
+"""Lightweight JS/TS source grouping rules."""
+
+BunSourcesInfo = provider(fields = ["transitive_sources"])
+
+
+def _bun_library_impl(ctx):
+    transitive_sources = [
+        dep[BunSourcesInfo].transitive_sources
+        for dep in ctx.attr.deps
+        if BunSourcesInfo in dep
+    ]
+    all_sources = depset(
+        direct = ctx.files.srcs,
+        transitive = transitive_sources,
+    )
+    return [
+        BunSourcesInfo(transitive_sources = all_sources),
+        DefaultInfo(files = all_sources),
+    ]
+
+
+js_library = rule(
+    implementation = _bun_library_impl,
+    attrs = {
+        "srcs": attr.label_list(
+            allow_files = [".js", ".jsx", ".mjs", ".cjs"],
+        ),
+        "deps": attr.label_list(),
+    },
+)
+
+ts_library = rule(
+    implementation = _bun_library_impl,
+    attrs = {
+        "srcs": attr.label_list(
+            allow_files = [".ts", ".tsx"],
+        ),
+        "deps": attr.label_list(),
+    },
+)