fix: adjust month range in contributor heatmap to exclude current month (hiero-hackers#253)

Signed-off-by: MonaaEid <monaa_eid@hotmail.com>

Author: MonaaEid

outputs/charts/org/hiero-hackers/contributor_activity_heatmap.png

@@ -53,7 +53,10 @@ def _month_key(value: datetime) -> str:
 def _recent_month_keys(months_back: int) -> list[str]:
     """Return the most recent month labels, oldest first."""
     current_month = pd.Period(pd.Timestamp.now(tz="UTC"), freq="M")
-    return [str(period) for period in pd.period_range(end=current_month, periods=months_back, freq="M")]
+    # Shift back by 1 month so the range ends on the last fully completed month
+    last_completed_month = current_month - 1
+
+    return [str(period) for period in pd.period_range(end=last_completed_month, periods=months_back, freq="M")]
 
 
 def _activity_action(activity_type: str) -> str | None:

outputs/charts/org/hiero-ledger/contributor_activity_heatmap.png

@@ -2,8 +2,6 @@
 
 from __future__ import annotations
 
-from datetime import UTC, datetime
-
 import pandas as pd
 
 from hiero_analytics.analysis.contributor_heatmap import (
@@ -20,11 +18,14 @@
 def _ev(actor: str, activity_type: str, n: int, *, repo: str = "o/x") -> ContributorActivityRecord:
     """Build a contributor-activity record dated to now (inside the heatmap window)."""
     target_type = "issue" if activity_type == "authored_issue" else "pull_request"
+
+    last_month_timestamp = pd.Timestamp.now(tz="UTC") - pd.DateOffset(months=1)
+
     return ContributorActivityRecord(
         repo=repo,
         activity_type=activity_type,
         actor=actor,
-        occurred_at=datetime.now(UTC),
+        occurred_at=last_month_timestamp.to_pydatetime(),
         target_type=target_type,
         target_number=n,
     )