feat(elisp): add coverage-summary to the Elisp bundle with missing-file detection

A line-weighted coverage total has a blind spot: a module no test loads never shows up in the SimpleCov report, so it can't drag the number down. The suite looks healthier than it is. This adds a summary that counts every source file on disk against the report and treats an absent file as 0%, weighting the project number by file instead of by line so untested modules stay visible.

The script ships at languages/elisp/claude/scripts/coverage-summary.el, self-contained on stock Emacs (just the built-in json). It parses the undercover SimpleCov shape directly rather than depending on the editor's coverage engine, so it runs anywhere the bundle lands. I proved it against a real 103-file report: 93 tracked, 27 untested modules surfaced, project number 66.4%.

Delivery follows the bundle convention. The script lives under the gitignored .claude/ footprint and gets auto-fixed on drift by sync-language-bundle.sh, which I made generic for any claude/scripts/* rather than coverage-specific. The Makefile targets ship as a project-owned fragment (languages/elisp/coverage-makefile.txt) that install-lang.sh seeds at the project root and sync drops into .ai/inbox/ when that convention exists. The bundle never edits the project's own Makefile.

Tests: 12 ERT for the kernel (Normal/Boundary/Error per function), wired into make test via a new languages/*/tests/ discovery path, plus bats for the sync auto-fix and the inbox-drop guards.

This is the Elisp pilot. The pattern is proven, so fanning out to Python, Go, and TypeScript is now a follow-up. Each one needs only its own parser and fragment. The plumbing is already generic.

1 files changed, 6 insertions, 0 deletions

diff --git a/languages/elisp/claude/rules/elisp-testing.md b/languages/elisp/claude/rules/elisp-testing.md
index b727cbd..7c3a9ef 100644
--- a/languages/elisp/claude/rules/elisp-testing.md
+++ b/languages/elisp/claude/rules/elisp-testing.md
@@ -37,6 +37,12 @@ Every non-trivial function needs at least:
 
 Missing a category is a test gap. If three cases look near-identical, parametrize with a loop or `dolist` rather than copy-pasting.
 
+### Measuring it — `make coverage-summary`
+
+The bundle ships a coverage summary at `.claude/scripts/coverage-summary.el` and a Makefile fragment (`coverage-makefile.txt`) with `coverage` and `coverage-summary` targets. After `make coverage` writes an undercover SimpleCov report, `make coverage-summary` prints a per-file table and a unit-weighted project number.
+
+The number to watch is the missing-file count. A module no test loads never appears in the SimpleCov report, so a line-weighted total skips it silently — the suite looks healthier than it is. The summary counts every `modules/*.el` on disk that's absent from the report as 0%, so an untested module drags the project number down where you can see it. Copy the fragment's targets into your own Makefile to adopt it; the bundle never edits your Makefile.
+
 ## TDD Workflow
 
 Write the failing test first. A failing test proves you understand the change. Assume the bug is in production code until the test proves otherwise — never fix the test before proving the test is wrong.