fix: shell-quote F6 test-runner command arguments

`cj/--f6-test-runner-cmd-for` was building shell command strings with raw paths and stems via `format`. For ordinary names (`tests/test_foo.py`, `pkg/foo`) that worked fine. But a path with spaces or a stem with shell metacharacters would break or misbehave once the string hit `compile`. A Python test file under `dir with spaces/` would get tokenized as separate arguments.

I added `cj/--f6-shell-quote-argument` that escapes only when the argument doesn't match `cj/--f6-shell-safe-argument-regexp` (alphanumerics, slash, dot, dash, plus a small handful of safe punctuation). Ordinary paths skip the quoter and stay readable. Risky paths route through `shell-quote-argument`.

I wrapped the four interpolations in the test-runner builder: the elisp `FILE=` basename, the elisp `TEST=^test-stem-` regex, both pytest paths, and the Go `./rel-dir`. The Go branch also handles an empty rel-dir explicitly so the result stays `go test ./` instead of constructing `./` via format with an empty string.

I added three boundary tests: a Python path with spaces, an elisp stem with `;`, and a Go directory with spaces. Existing tests for ordinary paths continue to pass since the safe regex covers them.

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/test-dev-fkeys--f6-test-runner-cmd-for.el b/tests/test-dev-fkeys--f6-test-runner-cmd-for.el
index cb242889..36f97548 100644
--- a/tests/test-dev-fkeys--f6-test-runner-cmd-for.el
+++ b/tests/test-dev-fkeys--f6-test-runner-cmd-for.el
@@ -95,6 +95,27 @@ would over-match. Pass just the basename — the Makefile re-prepends
             'go nil "main.go" "main" "")
            "go test ./")))
 
+(ert-deftest test-dev-fkeys-f6-cmd-for-python-test-file-quotes-spaces ()
+  "Boundary: a Python test file path with spaces is shell-escaped."
+  (should (string=
+           (cj/--f6-test-runner-cmd-for
+            'python t "tests/dir with spaces/test_foo.py" "foo" "tests/dir with spaces")
+           "pytest tests/dir\\ with\\ spaces/test_foo.py")))
+
+(ert-deftest test-dev-fkeys-f6-cmd-for-elisp-source-quotes-test-regex ()
+  "Boundary: an elisp source stem with shell metacharacters is escaped."
+  (should (string=
+           (cj/--f6-test-runner-cmd-for
+            'elisp nil "modules/foo;bar.el" "foo;bar" "modules")
+           "make test-name TEST=\\^test-foo\\;bar-")))
+
+(ert-deftest test-dev-fkeys-f6-cmd-for-go-source-quotes-spaces ()
+  "Boundary: a Go package path with spaces is shell-escaped."
+  (should (string=
+           (cj/--f6-test-runner-cmd-for
+            'go nil "pkg/with spaces/foo.go" "foo" "pkg/with spaces")
+           "go test ./pkg/with\\ spaces")))
+
 ;;; Error Cases
 
 (ert-deftest test-dev-fkeys-f6-cmd-for-typescript-returns-nil ()