fix(sync-check): ignore generated python and elisp artifacts

Pre-commit caught a false-positive on its first real-world run. The
.ai/scripts/__pycache__ directory created by make test (pytest writes
.pyc and .pytest_cache, emacs writes .elc) was flagged as drift
against the canonical's clean tree.

Added matching --exclude patterns to the diff -rq check and the --fix
rsync calls. Patterns: __pycache__, *.pyc, *.pyo, .pytest_cache, *.elc.
The --fix excludes prevent rsync's --delete from wiping the mirror's
__pycache__ when the canonical has none.

Four new bats tests cover the exclusions. All 12 pass.

2 files changed, 54 insertions, 4 deletions

diff --git a/scripts/sync-check.sh b/scripts/sync-check.sh
index 8fb9ab0..cc7bc62 100755
--- a/scripts/sync-check.sh
+++ b/scripts/sync-check.sh
@@ -35,12 +35,23 @@ fi
 
 paths=(protocols.org workflows scripts)
 
+# Generated artifacts that should never count as drift. These appear on the
+# mirror side when tests run (pytest writes .pyc and .pytest_cache; emacs
+# writes .elc) but aren't part of the canonical source.
+exclude_args=(
+    --exclude='__pycache__'
+    --exclude='*.pyc'
+    --exclude='*.pyo'
+    --exclude='.pytest_cache'
+    --exclude='*.elc'
+)
+
 check_drift() {
     local drift=0
     for relpath in "${paths[@]}"; do
-        if ! diff -rq "$canonical/$relpath" "$mirror/$relpath" >/dev/null 2>&1; then
+        if ! diff -rq "${exclude_args[@]}" "$canonical/$relpath" "$mirror/$relpath" >/dev/null 2>&1; then
             echo "drift: claude-templates/.ai/$relpath ↔ .ai/$relpath" >&2
-            diff -rq "$canonical/$relpath" "$mirror/$relpath" 2>&1 | head -20 >&2
+            diff -rq "${exclude_args[@]}" "$canonical/$relpath" "$mirror/$relpath" 2>&1 | head -20 >&2
             drift=1
         fi
     done
@@ -54,9 +65,18 @@ fi
 if [ "${1:-}" = "--fix" ]; then
     echo "" >&2
     echo "sync-check --fix: syncing canonical → mirror..." >&2
+    # Same exclude patterns as the diff so generated files in the mirror
+    # aren't wiped by --delete when canonical has no counterpart.
+    rsync_excludes=(
+        --exclude='__pycache__'
+        --exclude='*.pyc'
+        --exclude='*.pyo'
+        --exclude='.pytest_cache'
+        --exclude='*.elc'
+    )
     rsync -a "$canonical/protocols.org" "$mirror/protocols.org"
-    rsync -a --delete "$canonical/workflows/" "$mirror/workflows/"
-    rsync -a --delete "$canonical/scripts/" "$mirror/scripts/"
+    rsync -a --delete "${rsync_excludes[@]}" "$canonical/workflows/" "$mirror/workflows/"
+    rsync -a --delete "${rsync_excludes[@]}" "$canonical/scripts/" "$mirror/scripts/"
     if check_drift; then
         echo "sync-check --fix: resolved." >&2
         echo "Re-stage the synced files and retry the commit." >&2
diff --git a/scripts/tests/sync-check.bats b/scripts/tests/sync-check.bats
index df775b3..17c9189 100644
--- a/scripts/tests/sync-check.bats
+++ b/scripts/tests/sync-check.bats
@@ -84,3 +84,33 @@ setup() {
     [ "$status" -eq 2 ]
     [[ "$output" == *"not inside a git checkout"* ]]
 }
+
+@test "generated Python artifacts in mirror don't count as drift" {
+    mkdir -p .ai/scripts/__pycache__
+    touch .ai/scripts/__pycache__/foo.cpython-314.pyc
+    touch .ai/scripts/some.pyc
+    run scripts/sync-check.sh
+    [ "$status" -eq 0 ]
+}
+
+@test "compiled elisp artifacts in mirror don't count as drift" {
+    touch .ai/scripts/foo.elc
+    run scripts/sync-check.sh
+    [ "$status" -eq 0 ]
+}
+
+@test "pytest cache in mirror doesn't count as drift" {
+    mkdir -p .ai/scripts/.pytest_cache
+    touch .ai/scripts/.pytest_cache/CACHEDIR.TAG
+    run scripts/sync-check.sh
+    [ "$status" -eq 0 ]
+}
+
+@test "--fix preserves generated artifacts in mirror" {
+    mkdir -p .ai/scripts/__pycache__
+    touch .ai/scripts/__pycache__/foo.cpython-314.pyc
+    echo "drift" > .ai/protocols.org
+    run scripts/sync-check.sh --fix
+    [ "$status" -eq 0 ]
+    [ -f .ai/scripts/__pycache__/foo.cpython-314.pyc ]
+}