feat(dev-fkeys): add F6 test runner menu (Phase 2a)

I extended `dev-fkeys.el` with the F6 dispatcher half of the spec. F6 prompts via `completing-read` between two candidates: "All tests" delegates to `projectile-test-project`, and "Current file's tests" detects the buffer's language by extension, derives the runner command, and pipes through `compile' from the projectile root. C-F6 is the fast path straight to "Current file's tests".

Per-language coverage:

- Elisp source files map to `make test-name TEST=^test-<stem>-`. Elisp test files run with `make test-file FILE=<rel-path>` so a per-helper file like `test-foo--bar.el' runs only its own tests.
- Python source files map to `pytest tests/test_<stem>.py'. Python test files run with `pytest <rel-path>'.
- Go runs the package containing the file: `go test ./<rel-dir>'. Source and test files use the same command since Go test scope is per-package. Limit: this runs every `_test.go' in the package, not just the buffer's file. Phase 2b can refine via test-name discovery.
- TypeScript and JavaScript are detected but punted for v1. The runner-command builder returns nil and the orchestrator signals a user-error rather than guessing.

The F6 binding moved from the Phase 1 stopgap (`projectile-test-project') to `cj/f6-test-runner'. C-F6 is newly bound to `cj/f6-current-file-tests'. M-F6 stays unbound, reserved for Phase 2b's "Run a test..." menu entry.

TDD: 68 new tests across 7 files. Production code split into small testable internals (`cj/--f6-language-detect', `cj/--f6-buffer-is-test-file-p', `cj/--f6-source-stem', `cj/--f6-test-runner-cmd-for', `cj/--f6-current-file-tests-impl') plus two thin interactive wrappers. Smoke tests confirm bindings register on load.

I also updated the module commentary with the Phase 2b plan, the capture-then-filter approach for tree-sitter discovery, and a pointer to Emacs bug #79687. The bug is the predicate-syntax mismatch that breaks `:match' / `:equal' / `:pred' queries on Emacs 30.2 with libtree-sitter 0.26. The fix lives on Emacs master (commit b0143530), targets Emacs 31, and has not been backported to the emacs-30 branch as of today. Phase 2b will use queries without predicates and filter results in Elisp, sidestepping the issue. Mike Olson's `treesit-predicate-rewrite.el' applies the same idea to font-lock if you want it before Phase 2b lands.

1 files changed, 84 insertions, 0 deletions

diff --git a/tests/test-dev-fkeys--f6-source-stem.el b/tests/test-dev-fkeys--f6-source-stem.el
new file mode 100644
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+++ b/tests/test-dev-fkeys--f6-source-stem.el
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+;;; test-dev-fkeys--f6-source-stem.el --- Tests for cj/--f6-source-stem -*- lexical-binding: t -*-
+
+;;; Commentary:
+;; Tests for the stem extractor. Given any source-or-test filename, returns
+;; the source module name with directory, extension, and any test-pattern
+;; prefix/suffix stripped. Used to map source files to their tests and
+;; vice versa.
+
+;;; Code:
+
+(require 'ert)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'dev-fkeys)
+
+;;; Normal Cases — Elisp
+
+(ert-deftest test-dev-fkeys-f6-source-stem-elisp-source ()
+  "Normal: a regular elisp source file's stem is its basename."
+  (should (string= (cj/--f6-source-stem "modules/foo.el") "foo")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-elisp-test ()
+  "Normal: an elisp test file's stem strips the `test-' prefix."
+  (should (string= (cj/--f6-source-stem "tests/test-foo.el") "foo")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-elisp-test-double-dash ()
+  "Normal: an elisp per-helper test file `test-<module>--<helper>.el' yields
+the module name (everything from `--' onward is dropped)."
+  (should (string= (cj/--f6-source-stem "tests/test-dev-fkeys--detect-project-type.el")
+                   "dev-fkeys")))
+
+;;; Normal Cases — Python
+
+(ert-deftest test-dev-fkeys-f6-source-stem-python-source ()
+  "Normal: a regular Python source file's stem is its basename."
+  (should (string= (cj/--f6-source-stem "pkg/foo.py") "foo")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-python-test-prefix ()
+  "Normal: a `test_<name>.py' file's stem strips the `test_' prefix."
+  (should (string= (cj/--f6-source-stem "tests/test_foo.py") "foo")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-python-test-suffix ()
+  "Normal: a `<name>_test.py' file's stem strips the `_test' suffix."
+  (should (string= (cj/--f6-source-stem "pkg/foo_test.py") "foo")))
+
+;;; Normal Cases — Go
+
+(ert-deftest test-dev-fkeys-f6-source-stem-go-source ()
+  "Normal: a regular Go source file's stem is its basename."
+  (should (string= (cj/--f6-source-stem "pkg/foo.go") "foo")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-go-test ()
+  "Normal: a `<name>_test.go' file's stem strips the `_test' suffix."
+  (should (string= (cj/--f6-source-stem "pkg/foo_test.go") "foo")))
+
+;;; Boundary Cases
+
+(ert-deftest test-dev-fkeys-f6-source-stem-elisp-multi-segment-name ()
+  "Boundary: hyphenated module names round-trip cleanly."
+  (should (string= (cj/--f6-source-stem "modules/calendar-sync.el") "calendar-sync"))
+  (should (string= (cj/--f6-source-stem "tests/test-calendar-sync.el") "calendar-sync")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-elisp-test-with-dashes-after-double-dash ()
+  "Boundary: a per-helper test file with hyphens in both module and helper:
+`test-foo-bar--baz-qux.el' → `foo-bar' (stops at first `--')."
+  (should (string= (cj/--f6-source-stem "tests/test-foo-bar--baz-qux.el")
+                   "foo-bar")))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-unknown-language-falls-back-to-basename ()
+  "Boundary: an unsupported extension just returns the basename without extension."
+  (should (string= (cj/--f6-source-stem "foo.rs") "foo"))
+  (should (string= (cj/--f6-source-stem "foo.txt") "foo")))
+
+;;; Error Cases
+
+(ert-deftest test-dev-fkeys-f6-source-stem-nil-returns-nil ()
+  "Error: nil filename returns nil without erroring."
+  (should (null (cj/--f6-source-stem nil))))
+
+(ert-deftest test-dev-fkeys-f6-source-stem-empty-returns-nil ()
+  "Error: empty string returns nil."
+  (should (null (cj/--f6-source-stem ""))))
+
+(provide 'test-dev-fkeys--f6-source-stem)
+;;; test-dev-fkeys--f6-source-stem.el ends here