fix: resolve 17 P2 defects and 5 P3 defects from pre-launch audit

Batch fix covering multiple modules:
- P2-01: HandRegistry Semaphore-based max_concurrent enforcement
- P2-03: Populate toolCount/metricCount from Hand trait methods
- P2-06: heartbeat_update_config minimum interval validation
- P2-07: ReflectionResult used_fallback marker for rule-based fallback
- P2-08/09: identity_propose_change parameter naming consistency
- P2-10: ClassroomMetadata is_placeholder flag for LLM failure
- P2-11: classroomStore userDidCloseDuringGeneration intent tracking
- P2-12: workflowStore pipeline_create sends actionType
- P2-13/14: PipelineInfo step_count + PipelineStepInfo for proper step mapping
- P2-15: Pipe transform support in context.resolve (8 transforms)
- P2-16: Mustache {{...}} → \${...} auto-normalization
- P2-17: SaaSLogin password placeholder 6→8
- P2-19: serialize_skill_md + update_skill preserve tools field
- P2-22: ToolOutputGuard sensitive patterns from warn→block
- P2-23: Mutex::unwrap() → unwrap_or_else in relay/service.rs
- P3-01/03/07/08/09: Various P3 fixes
- DEFECT_LIST.md: comprehensive status sync (43/51 fixed, 8 remaining)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/zclaw-skills/src/registry.rs

@@ -238,6 +238,8 @@ impl SkillRegistry {
             tags: if updates.tags.is_empty() { existing.tags } else { updates.tags },
             category: updates.category.or(existing.category),
             triggers: if updates.triggers.is_empty() { existing.triggers } else { updates.triggers },
+            // P2-19: Preserve tools field during update (was silently dropped)
+            tools: if updates.tools.is_empty() { existing.tools } else { updates.tools },
             enabled: updates.enabled,
         };
 
@@ -296,6 +298,13 @@ fn serialize_skill_md(manifest: &SkillManifest) -> String {
     if !manifest.tags.is_empty() {
         parts.push(format!("tags: {}", manifest.tags.join(", ")));
     }
+    // P2-19: Serialize tools field (was missing, causing tools to be lost on re-serialization)
+    if !manifest.tools.is_empty() {
+        parts.push("tools:".to_string());
+        for tool in &manifest.tools {
+            parts.push(format!("  - \"{}\"", tool));
+        }
+    }
     if !manifest.triggers.is_empty() {
         parts.push("triggers:".to_string());
         for trigger in &manifest.triggers {