feat(typescript): add coverage-summary to the TypeScript bundle

Last language in the coverage-summary fan-out, after Elisp, Python, and Go. Same kernel: count every source file on disk that's absent from the coverage report as 0% and weight the project number by file, so an untested file stays visible instead of being averaged away.

The script at languages/typescript/claude/scripts/coverage-summary.js parses an Istanbul json-summary report (the coverage-summary.json that c8, Vitest, and Jest all emit), takes per-file statements covered over total, and reports a file-weighted number plus the missing files. It walks the source dir for .ts/.js, skipping test files, declarations, and node_modules. Node built-ins only, so it runs via node with no install, and it doesn't reimplement the per-file table nyc already prints.

Tests are black-box, run with node's own test runner: a temp tree plus a json-summary report, the script invoked via node, output asserted. They cover missing-file detection, all-tracked, test-file and node_modules exclusion, and the missing-report error. make test gained a node --test discovery path for languages/*/tests, guarded so environments without Node skip it cleanly. As with Python, the TypeScript bundle had no gitignore-add.txt, which would have left the script un-gitignored on install, so I added one.

This finishes the fan-out: coverage-summary now ships in all four bundles, each parsing its own tool's report behind the same file-weighted, missing-as-0% kernel. I proved the Go and TypeScript scripts by running them (Go against a live profile, TS against a synthetic report and the CLI). Python and TypeScript weren't run against a live coverage tool, since neither coverage.py nor nyc is installed here, so the first adopter of each should check against a real report.

1 files changed, 10 insertions, 0 deletions

diff --git a/scripts/tests/install-lang.bats b/scripts/tests/install-lang.bats
index a9f3bfe..0fb83e3 100644
--- a/scripts/tests/install-lang.bats
+++ b/scripts/tests/install-lang.bats
@@ -69,6 +69,16 @@ teardown() {
   grep -qxF "coverage.json" "$PROJECT/.gitignore"
 }
 
+@test "install-lang typescript: lands the coverage script in the gitignored footprint" {
+  run bash "$INSTALL_LANG" typescript "$PROJECT"
+
+  [ "$status" -eq 0 ]
+  [ -f "$PROJECT/.claude/scripts/coverage-summary.js" ]
+  [ -f "$PROJECT/coverage-makefile.txt" ]
+  grep -qxF ".claude/" "$PROJECT/.gitignore"
+  grep -qxF "coverage/" "$PROJECT/.gitignore"
+}
+
 @test "install-lang go: coverage-only slice lands without a CLAUDE.md" {
   run bash "$INSTALL_LANG" go "$PROJECT"