Rewrite the -count=1 note to match the current files (closes #77)

The note under the canonical Go `make test` example in `prompts/REPO_POLICIES.md` still named the cache-busting build argument that `--no-cache` replaced, and said Go's cache was baked into earlier image layers.

It now says where Go's test result cache can replay a pass: on a developer's machine, where the Makefile target runs, so `-count=1` stays on both invocations. The `test` phase of the `Dockerfile` has nothing to replay: its base image holds no result for the repo's tests and no earlier step runs one.

The first paragraph no longer says the rerun would replay a failure: Go stores only passes.

Model: opus-5-5

TODO.md

@@ -21,6 +21,12 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 2026-10-04: Rewrote the note under the canonical Go `make test` example in
+  `REPO_POLICIES.md` (issue 77), which still named the cache-busting build
+  argument that `--no-cache` replaced. It now says where Go's test result cache
+  can replay a pass: on a developer's machine, where the Makefile target runs,
+  and not in the `test` phase of the `Dockerfile`, whose base image and earlier
+  steps hold no result for the repo's tests.
 - 2026-10-04: The Makefile examples in the Go styleguide and the HTTP server
   conventions now fall back to `dev` when `git describe` prints nothing (outside
   a git checkout, or where git is missing or refuses the checkout), instead of