feat(stage16): implement observability — structured logging, metrics, tracing

- JSONFormatter, ContextVars, set_research_run_id() with short logger names
- self-built Counter/Histogram/Gauge system (no external deps)
- Prometheus text export at /metrics
- Request logging middleware with X-Request-ID
- Metrics instrumentation: search_queries, sources_fetched, claims, contradictions
- Histograms: research_duration, llm_request_duration
- Gauge: active_research_runs
- 13 + 21 = 34 tests

src/nsct/orchestration/orchestrator.py

@@ -18,6 +18,16 @@ from uuid import UUID, uuid4
 from nsct.agents.planner import MockResearchPlanner, ResearchPlanner
 from nsct.config import AppSettings
 from nsct.crawler.manager import CrawlerManager
+from nsct.logging_config import set_research_run_id, get_research_run_id, get_logger
+from nsct.metrics import (
+    metrics,
+    C_SEARCH_QUERIES_TOTAL,
+    C_SOURCES_FETCHED_TOTAL,
+    C_CLAIMS_EXTRACTED_TOTAL,
+    C_CONTRADICTIONS_DETECTED_TOTAL,
+    H_RESEARCH_DURATION,
+    H_LLM_REQUEST_DURATION,
+)
 from nsct.models.claim import Claim
 from nsct.orchestration.budget import BudgetExhaustedError, BudgetTracker, HardBudgetConfig
 from nsct.orchestration.models import ResearchRun
@@ -312,6 +322,9 @@ class ResearchOrchestrator:
         if self._run is None:
             await self.start()
 
+        # Record research start timestamp for duration histogram
+        _start = time.monotonic()
+
         # Pipeline-Schritte nacheinander
         steps = [
             "planning",
@@ -383,7 +396,11 @@ class ResearchOrchestrator:
             "budget_usage": self._budget_tracker.get_usage(),
         }
 
-        logger.info("Research pipeline completed: %d claims, state=%s", len(self._claims), report["state"])
+        elapsed = time.monotonic() - _start
+        metrics.observe(H_RESEARCH_DURATION, elapsed)
+
+        logger.info("Research pipeline completed: %d claims, state=%s, %.1fs",
+                    len(self._claims), report["state"], elapsed)
         return report
 
     async def run_step(self, step_name: str) -> dict[str, Any]:
@@ -428,6 +445,7 @@ class ResearchOrchestrator:
         """PLANNING: Erstelle Recherchestrategie mit dem Planner."""
         self._transition_to("planning")
 
+        llm_duration_start = time.monotonic()
         try:
             planner = self._get_planner()
             if isinstance(planner, MockResearchPlanner):
@@ -436,6 +454,9 @@ class ResearchOrchestrator:
             else:
                 self._budget_tracker.increment_llm_requests(1)
                 plan = await planner.plan(self._query, language="de")
+                # Track LLM request duration
+                elapsed = time.monotonic() - llm_duration_start
+                metrics.observe(H_LLM_REQUEST_DURATION, elapsed)
 
             self._plan = plan
 
@@ -514,6 +535,7 @@ class ResearchOrchestrator:
                     self._search_results.append(result_dict)
 
             logger.info("Search complete: %d unique URLs collected", len(self._search_results))
+            metrics.increment(C_SEARCH_QUERIES_TOTAL, len(plan_queries))
             return {"success": True, "data": {"urls": self._search_results}, "url_count": len(self._search_results)}
 
         except Exception as exc:
@@ -561,6 +583,7 @@ class ResearchOrchestrator:
                 self._budget_tracker.increment_download_bytes(content_len)
 
             successful = [s for s in self._sources if not s.get("error")]
+            metrics.increment(C_SOURCES_FETCHED_TOTAL, len(self._sources))
             logger.info("Fetching complete: %d/%d sources successfully fetched", len(successful), len(self._sources))
             return {
                 "success": True,
@@ -614,6 +637,7 @@ class ResearchOrchestrator:
                 )
 
             logger.info("Extraction complete: %d claims", len(self._claims))
+            metrics.increment(C_CLAIMS_EXTRACTED_TOTAL, len(self._claims))
             return {"success": True, "data": {"claims": [c.model_dump() for c in self._claims]}, "claim_count": len(self._claims)}
 
         except Exception as exc: