fix: eliminate all project warnings from JS build

- Added "supported-targets": "js" to 6 packages that depend on
  JS-only libraries (luna, mars, node/*)
- Prefixed 10 unused fields in actrun ActionManifestSpec with _
  to suppress unused_field warnings

Result: 0 warnings from project code.
Only 1 external warning remains (yacc duplicate alias - not fixable).
85 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mizchi

src/actrun/parser.mbt

@@ -1634,16 +1634,16 @@ priv struct ActionManifestSpec {
   inputs : Map[String, String]
   runtime : String
   steps : Array[StepSpec]
-  main : String
-  pre : String?
-  post : String?
-  pre_if : String
-  post_if : String
-  image : String
-  args : Array[String]
-  entrypoint : String?
-  pre_entrypoint : String?
-  post_entrypoint : String?
+  _main : String
+  _pre : String?
+  _post : String?
+  _pre_if : String
+  _post_if : String
+  _image : String
+  _args : Array[String]
+  _entrypoint : String?
+  _pre_entrypoint : String?
+  _post_entrypoint : String?
 }
 
 ///|
@@ -1768,16 +1768,16 @@ fn parse_action_manifest_yaml(text : String) -> ActionManifestParseResult {
         inputs,
         runtime: action_using,
         steps,
-        main,
-        pre,
-        post,
-        pre_if,
-        post_if,
-        image,
-        args,
-        entrypoint,
-        pre_entrypoint,
-        post_entrypoint,
+        _main: main,
+        _pre: pre,
+        _post: post,
+        _pre_if: pre_if,
+        _post_if: post_if,
+        _image: image,
+        _args: args,
+        _entrypoint: entrypoint,
+        _pre_entrypoint: pre_entrypoint,
+        _post_entrypoint: post_entrypoint,
       }),
       errors,
     }

src/adapters/mars_http/moon.pkg

@@ -6,3 +6,7 @@ import {
   "mizchi/sol" @sol,
   "bit-vcs/bithub/core" @core,
 }
+
+options(
+  "supported-targets": "js",
+)

src/cmd/bithub/moon.pkg

@@ -23,6 +23,7 @@ import {
 } for "test"
 
 options(
+  "supported-targets": "js",
   is_main: true,
   link: { "js": { "format": "cjs" } },
   targets: {

src/cmd/bithub_bench/moon.pkg

@@ -6,6 +6,7 @@ import {
 }
 
 options(
+  "supported-targets": "js",
   is_main: true,
   link: { "js": { "format": "cjs" } },
   targets: { "main.mbt": [ "js" ] },

src/cmd/main/moon.pkg

@@ -6,6 +6,7 @@ import {
 }
 
 options(
+  "supported-targets": "js",
   is_main: true,
   link: { "js": { "format": "esm", "exports": ["fetch"] } },
 )

src/cmd/main_fetch_ssr/moon.pkg

@@ -7,6 +7,7 @@ import {
 }
 
 options(
+  "supported-targets": "js",
   is_main: true,
   link: { "js": { "format": "cjs" } },
   targets: {

src/cmd/main_ssr/moon.pkg

@@ -6,6 +6,7 @@ import {
 }
 
 options(
+  "supported-targets": "js",
   is_main: true,
   link: { "js": { "format": "cjs" } },
   targets: {