restore(lang): full lang tree from ff3ef452 (306 files) — compiler, vm, shared, runner, c-abi, etc.\n\n- Restores lang/ directory (files≈306, dirs≈64) as per historical branch with selfhost sources\n- Keeps our recent parser index changes in compiler/* (merged clean by checkout)\n- Unblocks selfhost development and documentation references

lang/src/compiler/pipeline_v2/execution_pipeline_box.hako

@@ -37,9 +37,12 @@ box ExecutionPipelineBox {
     if stage3_flag == 1 { p.stage3_enable(1) }
     p.extract_usings(src)
     local usings = p.get_usings_json()
+    // Extract extern_c annotations (syntax: @extern_c("c_symbol","Func/Arity");)
+    p.extract_externs(src)
+    local externs = p.get_externs_json()
     local ast = p.parse_program2(src)
     // Emit Stage‑1 JSON with meta.usings
-    local json = EmitterBox.emit_program(ast, usings)
+    local json = EmitterBox.emit_program(ast, usings, externs)
     if json == null || json.size() == 0 { return 1 }
     print(json)
     return 0

lang/src/compiler/pipeline_v2/flow_entry.hako

@@ -2,6 +2,7 @@
 // Guard: This box performs no execution. Returns MIR(JSON) as text.
 
 using "lang/src/compiler/pipeline_v2/pipeline.hako" as PipelineV2
+using "lang/src/shared/json/mir_v1_adapter.hako" as MirJsonV1Adapter
 
 static box FlowEntryBox {
   // Emit legacy v0 JSON（call/boxcall/newbox）。最小入力: Stage‑1 JSON 文字列
@@ -21,6 +22,18 @@ static box FlowEntryBox {
     return PipelineV2.lower_stage1_to_mir_v1_compat(ast_json, prefer_cfg)
   }
 
+  // Emit v1 JSON with metadata.extern_c（externs を v1 の metadata に反映）
+  // externs_json: JSON array text, e.g. [{"func":"Name/Arity","symbol":"c_symbol"}]
+  emit_v1_from_ast_with_meta(ast_json, prefer_cfg, externs_json) {
+    return PipelineV2.lower_stage1_to_mir_v1_with_meta(ast_json, prefer_cfg, externs_json)
+  }
+
+  // Emit v1 JSON + metadata.extern_c を注入し、v0互換に変換
+  emit_v1_compat_from_ast_with_meta(ast_json, prefer_cfg, externs_json) {
+    local j1 = PipelineV2.lower_stage1_to_mir_v1_with_meta(ast_json, prefer_cfg, externs_json)
+    return MirJsonV1Adapter.to_v0(j1)
+  }
+
   // No-op entry（箱ガード用）
   main(args) { return 0 }
 }

lang/src/compiler/pipeline_v2/pipeline.hako

@@ -24,6 +24,7 @@ using "lang/src/compiler/pipeline_v2/stage1_name_args_normalizer_box.hako" as Na
 using "lang/src/compiler/pipeline_v2/alias_preflight_box.hako" as AliasPreflightBox
 using "lang/src/compiler/pipeline_v2/stage1_args_parser_box.hako" as Stage1ArgsParserBox
 using "lang/src/compiler/pipeline_v2/pipeline_helpers_box.hako" as PipelineHelpersBox
+using "lang/src/shared/json/mir_v1_meta_inject_box.hako" as MirV1MetaInjectBox
 
 flow PipelineV2 {
   lower_stage1_to_mir(ast_json, prefer_cfg) {
@@ -150,6 +151,14 @@ flow PipelineV2 {
     return PipelineV2.lower_stage1_to_mir(ast_json, prefer_cfg)
   }
 
+  // Experimental (with metadata): emit JSON v1 and inject metadata.extern_c.
+  // externs_json: JSON array text like
+  //   [{"func":"Name/Arity","symbol":"c_symbol"}, ...]
+  lower_stage1_to_mir_v1_with_meta(ast_json, prefer_cfg, externs_json) {
+    local j1 = PipelineV2.lower_stage1_to_mir_v1(ast_json, prefer_cfg)
+    return MirV1MetaInjectBox.inject_meta_externs(j1, externs_json)
+  }
+
   // Experimental helper: emit v1 then downgrade to v0 for Mini‑VM exec
   lower_stage1_to_mir_v1_compat(ast_json, prefer_cfg) {
     local j1 = PipelineV2.lower_stage1_to_mir_v1(ast_json, prefer_cfg)

lang/src/compiler/pipeline_v2/pipeline_emit_box.hako

@@ -3,6 +3,7 @@
 
 using "lang/src/compiler/pipeline_v2/emit_call_box.hako" as EmitCallBox
 using "lang/src/compiler/pipeline_v2/local_ssa_box.hako" as LocalSSABox
+using "lang/src/shared/json/mir_v1_meta_inject_box.hako" as MirV1MetaInjectBox
 
 static box PipelineEmitBox {
   // Emit Call(name, int-args) → JSON v0, wrapped with LocalSSA ensures
@@ -10,6 +11,14 @@ static box PipelineEmitBox {
     local j = EmitCallBox.emit_call_int_args(name, args)
     return LocalSSABox.ensure_calls(LocalSSABox.ensure_cond(j))
   }
+
+  // Emit Call(name, int-args) → JSON v1 with metadata.extern_c (if provided)
+  // externs_json: JSON array text like
+  //   [{"func":"Name/Arity","symbol":"c_symbol"}, ...]
+  emit_call_int_args_v1_with_meta(name, args, externs_json) {
+    local jv0 = me.emit_call_int_args_v0(name, args)
+    return MirV1MetaInjectBox.inject_meta_externs(jv0, externs_json)
+  }
 }
 
 static box PipelineEmitMain { main(args) { return 0 } }