Allow go test on one package while iterating (closes #51)

Follows sneak's ruling at
#51 (comment). An agent
whose work is confined to one package may run `go test` directly on that
package's suite, or on individual tests in it, while iterating. `go build`,
`go vet` and the linter still go through make targets. The full `make check`
is still required before every push. The `Makefile` gains nothing.

The rule on Docker now says the lint and test gates run there, because a run
while iterating is not a gate.

Model: opus-5-5

TODO.md

@@ -21,6 +21,13 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 2026-11-04: An agent whose work is confined to one package may run `go test`
+  directly on that package's suite, or on individual tests in it, while
+  iterating (https://git.eeqj.de/sneak/prompts/issues/51), on sneak's ruling at
+  https://git.eeqj.de/sneak/prompts/issues/51#issuecomment-167600. The full
+  `make check` is still required before every push, and the `Makefile` gains
+  nothing. The rule on Docker now names the lint and test gates, because a run
+  while iterating is not one.
 - 2026-11-04: node, yarn, npm, python, pip and venv now come from the
   distribution with no version and no hash
   (https://git.eeqj.de/sneak/prompts/issues/146), on sneak's ruling at

prompts/REPO_POLICIES.md

@@ -176,6 +176,12 @@ style conventions are in separate documents:
   instead of invoking the underlying tools directly. The Makefile is the single
   source of truth for how these operations are run.
 
+    An agent whose work is confined to one package may run `go test` directly on
+    that package's suite, or on individual tests in it, while iterating. This is
+    the only exception to this rule. `go build`, `go vet` and the linter still
+    go through make targets. A run while iterating is not a gate, so the full
+    `make check` is still required before every push.
+
 - The Makefile is authoritative documentation for how the repo is used. Beyond
   the required targets above, it should have targets for every common operation:
     - running a local development server (`make run`, `make dev`)
@@ -207,9 +213,9 @@ style conventions are in separate documents:
     and the dependency manifests it needs (`package.json` + `yarn.lock`,
     `go.mod` + `go.sum`, etc.) before running it.
 
-- **Linting and testing run in Docker, as phases of the `Dockerfile`.** There is
-  no separate lint file. `script/lint` and `script/test` each build one phase
-  and nothing else:
+- **The lint and test gates run in Docker, as phases of the `Dockerfile`.**
+  There is no separate lint file. `script/lint` and `script/test` each build one
+  phase and nothing else:
 
     ```sh
     docker build --build-arg CACHEBUST="$(date +%s)-$$" \