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/gc_controller.rs

@@ -7,6 +7,7 @@ use super::gc::{BarrierKind, GcHooks};
 use super::gc_mode::GcMode;
 use crate::config::env;
 use crate::runtime::gc_trace;
+use crate::runtime::get_global_ring0;
 use std::collections::{HashSet, VecDeque};
 
 pub struct GcController {
@@ -172,10 +173,10 @@ impl GcController {
                 self.trial_nodes_last.store(nodes, Ordering::Relaxed);
                 self.trial_edges_last.store(edges, Ordering::Relaxed);
                 if (nodes + edges) > 0 && crate::config::env::gc_metrics() {
-                    eprintln!(
+                    get_global_ring0().log.info(&format!(
                         "[GC] trial: reachable nodes={} edges={} (roots=jit_handles)",
                         nodes, edges
-                    );
+                    ));
                 }
                 // Update counters
                 let dur = started.elapsed();