fix(mir/builder): use function-local ValueId throughout MIR builder

Phase 25.1b: Complete SSA fix - eliminate all global ValueId usage in function contexts.

Root cause: ~75 locations throughout MIR builder were using global value
generator (self.value_gen.next()) instead of function-local allocator
(f.next_value_id()), causing SSA verification failures and runtime
"use of undefined value" errors.

Solution:
- Added next_value_id() helper that automatically chooses correct allocator
- Fixed 19 files with ~75 occurrences of ValueId allocation
- All function-context allocations now use function-local IDs

Files modified:
- src/mir/builder/utils.rs: Added next_value_id() helper, fixed 8 locations
- src/mir/builder/builder_calls.rs: 17 fixes
- src/mir/builder/ops.rs: 8 fixes
- src/mir/builder/stmts.rs: 7 fixes
- src/mir/builder/emission/constant.rs: 6 fixes
- src/mir/builder/rewrite/*.rs: 10 fixes
- + 13 other files

Verification:
- cargo build --release: SUCCESS
- Simple tests with NYASH_VM_VERIFY_MIR=1: Zero undefined errors
- Multi-parameter static methods: All working

Known remaining: ValueId(22) in Stage-B (separate issue to investigate)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lang/src/runner/launcher.hako

@@ -13,6 +13,7 @@
 
 using lang.mir.builder.MirBuilderBox
 using lang.compiler.build.build_box as BuildBox
+using selfhost.shared.host_bridge.codegen_bridge as CodegenBridgeBox
 
 static box HakoCli {
   // Entry from Main.main(args)
@@ -138,21 +139,14 @@ static box HakoCli {
     }
     local ms = "" + mir
 
-    local emit_args = new ArrayBox()
-    emit_args.push(ms)
-    local obj = hostbridge.extern_invoke("env.codegen", "emit_object", emit_args)
+    local obj = CodegenBridgeBox.emit_object(ms)
     if obj == null || ("" + obj) == "" {
       print("[hakorune] build exe: env.codegen.emit_object failed")
       return 91
     }
     local obj_path = "" + obj
 
-    local link_args = new ArrayBox()
-    link_args.push(obj_path)
-    if out_path != null && out_path != "" {
-      link_args.push(out_path)
-    }
-    local exe = hostbridge.extern_invoke("env.codegen", "link_object", link_args)
+    local exe = CodegenBridgeBox.link_object(obj_path, out_path)
     if exe == null || ("" + exe) == "" {
       print("[hakorune] build exe: env.codegen.link_object failed")
       return 91