test: add bats test suite for lib/ helper scripts

110 tests across 10 test files covering all lib/ scripts:
- archeflow-event.sh: JSONL format, seq numbering, parent fields, validation
- archeflow-memory.sh: add/list/decay/forget/inject/extract commands
- archeflow-git.sh: branch creation, commit format, merge strategies, safety
- archeflow-report.sh: markdown output, summary mode, in-progress handling
- archeflow-progress.sh: progress.md generation, JSON mode, error handling
- archeflow-score.sh: archetype scoring, effectiveness report, validation
- archeflow-dag.sh: DAG rendering, color flags, tree structure
- archeflow-rollback.sh: arg parsing, phase validation, mutual exclusivity
- archeflow-init.sh: template listing, clone from project, arg validation
- archeflow-review.sh: diff modes, stats, branch/commit range review

Includes test_helper.bash (shared setup/teardown with temp git repos)
and scripts/run-tests.sh runner.

tests/test_helper.bash

@@ -0,0 +1,40 @@
+# test_helper.bash — Shared setup/teardown for ArcheFlow bats tests.
+#
+# Usage in .bats files:
+#   setup()    { load test_helper; _common_setup; }
+#   teardown() { _common_teardown; }
+#
+# Provides:
+#   - BATS_TEST_TMPDIR: unique temp directory per test
+#   - Mock .archeflow/ structure via a git repo
+#   - LIB_DIR: path to the lib/ scripts under test
+
+LIB_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/../lib" && pwd)"
+
+_common_setup() {
+  # Create a unique temp directory for this test
+  BATS_TEST_TMPDIR="$(mktemp -d)"
+  export BATS_TEST_TMPDIR
+
+  # Work inside the temp dir so scripts create .archeflow/ there
+  cd "$BATS_TEST_TMPDIR"
+
+  # Initialize a minimal git repo (many scripts need it)
+  git init --quiet
+  git config user.email "test@test.com"
+  git config user.name "Test User"
+  # Disable commit signing in tests (global config may have it enabled)
+  git config commit.gpgsign false
+  git config tag.gpgsign false
+
+  # Create an initial commit so HEAD exists
+  echo "init" > README.md
+  git add README.md
+  git commit -m "init" --quiet
+}
+
+_common_teardown() {
+  # Return to a safe directory before cleanup
+  cd /tmp
+  rm -rf "$BATS_TEST_TMPDIR"
+}