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/runner.rs

@@ -9,6 +9,14 @@ use zclaw_types::Result;
 
 use super::{Skill, SkillContext, SkillManifest, SkillResult};
 
+/// Returns the platform-appropriate Python binary name.
+/// On Windows, the standard installer provides `python.exe`, not `python3.exe`.
+#[cfg(target_os = "windows")]
+fn python_bin() -> &'static str { "python" }
+
+#[cfg(not(target_os = "windows"))]
+fn python_bin() -> &'static str { "python3" }
+
 /// Prompt-only skill execution
 pub struct PromptOnlySkill {
     manifest: SkillManifest,
@@ -80,7 +88,8 @@ impl Skill for PythonSkill {
         let start = Instant::now();
         let input_json = serde_json::to_string(&input).unwrap_or_default();
 
-        let output = Command::new("python3")
+        // P2-20: Platform-aware Python binary (Windows has no python3)
+        let output = Command::new(python_bin())
             .arg(&self.script_path)
             .env("SKILL_INPUT", &input_json)
             .env("AGENT_ID", &context.agent_id)
@@ -158,14 +167,27 @@ impl Skill for ShellSkill {
                 .map_err(|e| zclaw_types::ZclawError::ToolError(format!("Failed to execute shell: {}", e)))?
         };
 
-        let _duration_ms = start.elapsed().as_millis() as u64;
+        // P3-08: Use duration_ms instead of discarding it
+        let duration_ms = start.elapsed().as_millis() as u64;
 
         if output.status.success() {
             let stdout = String::from_utf8_lossy(&output.stdout);
-            Ok(SkillResult::success(Value::String(stdout.to_string())))
+            Ok(SkillResult {
+                success: true,
+                output: Value::String(stdout.to_string()),
+                error: None,
+                duration_ms: Some(duration_ms),
+                tokens_used: None,
+            })
         } else {
             let stderr = String::from_utf8_lossy(&output.stderr);
-            Ok(SkillResult::error(stderr))
+            Ok(SkillResult {
+                success: false,
+                output: Value::Null,
+                error: Some(stderr.to_string()),
+                duration_ms: Some(duration_ms),
+                tokens_used: None,
+            })
         }
     }
 }