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/runner/modes/vm.rs

@@ -587,8 +587,13 @@ impl NyashRunner {
                 // Quiet mode: suppress "RC:" output for JSON-only pipelines
                 if !quiet_pipe {
                     // Phase 98: ConsoleService if available, otherwise eprintln
+                    // Phase 103: Handle Option<Arc<dyn ConsoleService>>
                     if let Some(host) = crate::runtime::try_get_core_plugin_host() {
-                        host.core.console.println(&format!("RC: {}", exit_code));
+                        if let Some(ref console) = host.core.console {
+                            console.println(&format!("RC: {}", exit_code));
+                        } else {
+                            println!("RC: {}", exit_code);
+                        }
                     } else {
                         println!("RC: {}", exit_code);
                     }