fix: release script exits silently when grep finds no matches

The changelog grep commands return exit code 1 when no commits match,
which set -euo pipefail treats as fatal. Add || true guards so the
script continues to the tag/push/release steps.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

script/release

@@ -109,10 +109,10 @@ fi
 MERGE_RE="^(storkit|story-kit): merge "
 if [ -n "$LOG_RANGE" ]; then
   MERGED_RAW=$(git log "$LOG_RANGE" --pretty=format:"%s" --no-merges \
-    | grep -E "$MERGE_RE" | sed -E "s/$MERGE_RE//" | sort -u)
+    | grep -E "$MERGE_RE" | sed -E "s/$MERGE_RE//" | sort -u || true)
 else
   MERGED_RAW=$(git log --pretty=format:"%s" --no-merges \
-    | grep -E "$MERGE_RE" | sed -E "s/$MERGE_RE//" | sort -u)
+    | grep -E "$MERGE_RE" | sed -E "s/$MERGE_RE//" | sort -u || true)
 fi
 
 # Categorise merged work items and format names.
@@ -138,13 +138,13 @@ if [ -n "$LOG_RANGE" ]; then
     | grep -Ev "^(storkit|story-kit): " \
     | grep -Ev "^Revert \"(storkit|story-kit): " \
     | grep -v "^Bump version" \
-    | sed 's/^/- /')
+    | sed 's/^/- /' || true)
 else
   MANUAL=$(git log --pretty=format:"%s" --no-merges \
     | grep -Ev "^(storkit|story-kit): " \
     | grep -Ev "^Revert \"(storkit|story-kit): " \
     | grep -v "^Bump version" \
-    | sed 's/^/- /')
+    | sed 's/^/- /' || true)
 fi
 
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