Enable focused tests as repository pre-commit hook

.githooks/pre-commit

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+# Repository pre-commit hook: run only tests selected by staged paths.
+set -euo pipefail
+
+REPO_ROOT="$(git rev-parse --show-toplevel)"
+exec "$REPO_ROOT/scripts/test-changed.sh"

docs/Architecture/Testing Policy.md

@@ -22,11 +22,18 @@ For normal commits, use the focused wrapper:
 ```
 
 It reads staged paths with `git diff --cached` and runs only the mapped Bats
-files. Use `--list` to inspect the selection without running tests, or
-`--paths FILE ...` to preview a mapping. Shared test infrastructure and
-unmapped paths fail closed rather than silently skipping coverage. Run the
-full suite with `./tests/run.sh` when changing shared test helpers, the test
-runner, or when focused coverage is not sufficient.
+files. The tracked `.githooks/pre-commit` hook invokes this wrapper. Enable the
+repository hook path once per checkout:
+
+```bash
+git config core.hooksPath .githooks
+```
+
+Use `--list` to inspect the selection without running tests, or `--paths FILE
+...` to preview a mapping. Shared test infrastructure and unmapped paths fail
+closed rather than silently skipping coverage. Run the full suite with
+`./tests/run.sh` when changing shared test helpers, the test runner, or when
+focused coverage is not sufficient.
 
 ## Red-Green
 

scripts/test-changed.sh

@@ -76,6 +76,9 @@ for path in "${CHANGED[@]}"; do
         tests/helpers.bash|tests/run.sh)
             die "$path is shared test infrastructure; run ./tests/run.sh explicitly"
             ;;
+        .githooks/*)
+            add_test tests/changed_tests.bats
+            ;;
         dankserver/compose.yaml|dankclaw/compose.yaml)
             add_test tests/compose_validity.bats
             add_test tests/env_consistency.bats

tests/changed_tests.bats

@@ -6,6 +6,9 @@ load helpers
 
 @test "changed-test wrapper is executable and uses staged diff by default" {
     [ -x "$REPO_ROOT/scripts/test-changed.sh" ]
+    [ -x "$REPO_ROOT/.githooks/pre-commit" ]
+    run grep -F 'scripts/test-changed.sh' "$REPO_ROOT/.githooks/pre-commit"
+    [ "$status" -eq 0 ]
     run grep -F 'git diff --cached' "$REPO_ROOT/scripts/test-changed.sh"
     [ "$status" -eq 0 ]
 }