Keep make test from collecting tests in nested checkouts (closes #25)

vitest does not read .gitignore when finding tests, so a checkout nested
under .claude/ had its whole test/ tree run as part of this suite.
vitest.config.ts adds .claude/** to vitest's default excludes. The new
packaging test plants a nested checkout in a temp directory and fails if
vitest, run with this config, would collect it.

Model: opus-5-5

TODO.md

@@ -18,6 +18,12 @@ Tag v1.0.0.
 
 # Completed Steps
 
+- 2026-09-22: Stopped `make test` collecting tests from checkouts nested under
+  `.claude/` (issue 25). vitest ignores `.gitignore` when finding tests, so a
+  nested checkout ran the whole suite again; `vitest.config.ts` now adds
+  `.claude/**` to vitest's default excludes, and
+  `test/packaging/nested-checkout.test.ts` plants a nested checkout in a temp
+  directory and fails if vitest would collect it.
 - 2026-09-22: Rewrote the README API reference (and the Getting Started / usage
   snippets) to match the shipped cache/API library on `next` (issue 53, issue
   13). Documented `Library.open` and its options, the default-read vs `fresh()`