feat(runtime): Phase 103 CoreServices Optional化 - Memory Constraints対応

- Add CoreServicesConfig struct (from_env, minimal, all_enabled)
- Implement with_core_from_registry_optional() for selective initialization
- Update CoreBoxesImpl fields to Option<Arc<dyn XyzService>>
- Maintain backward compatibility (with_core_from_registry calls all_enabled)
- Add NYASH_CORE_DISABLE_* environment variable support
- ConsoleBox remains mandatory (Graceful Degradation principle)
- Add unit tests for optional initialization
- Update console_println! macro to handle Option type
- Fix direct console.println() calls in vm.rs and selfhost.rs
- Create core_optional_design.md documentation

Note: Phase 104 will extend ConsoleService to be optional as well with
graceful fallback in console_println! macro.

Files modified:
- src/runtime/plugin_host.rs (CoreServicesConfig, with_core_from_registry_optional, tests)
- src/runtime/core_services.rs (CoreBoxesImpl fields → Option type)
- src/runtime/mod.rs (console_println! macro updated)
- src/runner/modes/vm.rs (handle Option console)
- src/runner/selfhost.rs (handle Option console)
- docs/development/current/main/core_optional_design.md (new)
- docs/development/current/main/ring0-inventory.md (Phase 103 entry)

Test results:
- Build: ✅ Success (0 errors, 7 warnings)
- Unit tests: ✅ 3/3 passed (optional_core_tests)
- Runtime tests: ✅ 63/63 passed
- Smoke tests: ✅ 30/31 passed (1 pre-existing timeout)

src/runtime/plugin_loader_v2/enabled/loader/library.rs

@@ -3,6 +3,7 @@ use super::util::dbg_on;
 use super::PluginLoaderV2;
 use crate::bid::{BidError, BidResult};
 use crate::config::nyash_toml_v2::LibraryDefinition;
+use crate::runtime::get_global_ring0;
 use libloading::{Library, Symbol};
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
@@ -45,19 +46,19 @@ pub(super) fn load_plugin(
     }
     let lib_path = lib_path.unwrap_or_else(|| base.to_path_buf());
     if dbg_on() {
-        eprintln!(
+        get_global_ring0().log.debug(&format!(
             "[PluginLoaderV2] load_plugin: lib='{}' path='{}'",
             lib_name,
             lib_path.display()
-        );
+        ));
     }
     let lib = unsafe { Library::new(&lib_path) }.map_err(|e| {
-        eprintln!(
+        get_global_ring0().log.error(&format!(
             "[plugin/init] dlopen failed for {} ({}): {}",
             lib_name,
             lib_path.display(),
             e
-        );
+        ));
         BidError::PluginError
     })?;
     let lib_arc = Arc::new(lib);
@@ -90,12 +91,12 @@ pub(super) fn load_plugin(
             {
                 specs::record_typebox_spec(loader, lib_name, box_type, &*tb_sym)?;
             } else if dbg_on() {
-                eprintln!(
+                get_global_ring0().log.debug(&format!(
                     "[PluginLoaderV2] NOTE: TypeBox symbol not found for {}.{} (symbol='{}'). Migrate plugin to Nyash ABI v2 to enable per-Box dispatch.",
                     lib_name,
                     box_type,
                     sym_name.trim_end_matches('\0')
-                );
+                ));
             }
         }
     }