fix(gate): --brief leaves the test database's own log out of an excerpt

The DB lane provokes constraint errors on purpose, and their ERROR: lines
from the testdb container came first in a red pytest excerpt, ahead of the
failing test (seen in E35 S3). The excerpt now skips the testdb-N lines.

frontend/src/lib/gates.snapshot.json

@@ -1392,7 +1392,8 @@
       "}",
       "brief_excerpt() {",
       "  local hits",
-      "  hits=\"$(grep -E -i -A 2 -m 20 'error|fail|✗|×|warn|would reformat|unused|vulnerab|found [0-9]' \"$1\")\"",
+      "  hits=\"$(grep -v -E '^testdb-[0-9]+ ' \"$1\" |",
+      "    grep -E -i -A 2 -m 20 'error|fail|✗|×|warn|would reformat|unused|vulnerab|found [0-9]')\"",
       "  if [ -n \"$hits\" ]; then printf '%s\\n' \"$hits\"; else tail -n 20 \"$1\"; fi",
       "}",
       "ruff_pinned() {",

scripts/check.sh

@@ -50,10 +50,13 @@ lane() { # lane <name> <command…> — run it, remember a failure, never stop
 }
 # The lines that say what broke: the first 20 error-looking ones, each with the two lines after it
 # (knip names the file on the line after "Unused files"); a log with none of them (a tool that
-# words its failures some other way) shows its tail instead, which is where a summary sits.
+# words its failures some other way) shows its tail instead, which is where a summary sits. The test
+# database's own log is left out: the DB lane provokes constraint errors on purpose, and its
+# `ERROR:` lines filled the excerpt ahead of the failing test.
 brief_excerpt() {
   local hits
-  hits="$(grep -E -i -A 2 -m 20 'error|fail|✗|×|warn|would reformat|unused|vulnerab|found [0-9]' "$1")"
+  hits="$(grep -v -E '^testdb-[0-9]+ ' "$1" |
+    grep -E -i -A 2 -m 20 'error|fail|✗|×|warn|would reformat|unused|vulnerab|found [0-9]')"
   if [ -n "$hits" ]; then printf '%s\n' "$hits"; else tail -n 20 "$1"; fi
 }