Keep agent guidance in one root AGENTS.md (closes #31)

The canonical REPO_POLICIES.md now says that guidance for coding agents lives in one AGENTS.md at the repository root, including anything an agent should remember between sessions, and is never committed under a file or directory named after one agent tool or split into separate memory files. This retires the in-repo memory rule that older vendored copies still carry.

AGENTS.md is added to the list of files allowed in the root, which would otherwise contradict the new rule. Both checklists carry the matching item.

Model: opus-5-5

TODO.md

@@ -27,12 +27,6 @@ fmt-check, and commit.
   31). This retires the rule, still present in older vendored copies, that kept
   agent memory as committed files under `.claude/memory/`. `AGENTS.md` joins the
   list of files allowed in the root, and both checklists say so.
-- 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

prompts/REPO_POLICIES.md

@@ -317,19 +317,17 @@ style conventions are in separate documents:
     ```
 
     `-count=1` is required on both invocations: it defeats Go's test _result_
-    cache, so neither run can report a stored pass in place of running the
+    cache, so the target cannot report a pass it did not earn, and the rerun
-    tests. It leaves the build cache alone, so it costs the runtime of the suite
+    reproduces a failure instead of replaying it. It leaves the build cache
-    and no recompilation.
+    alone, so it costs the runtime of the suite and no recompilation.
 
-    That cache is Go's own, separate from Docker's layer cache. Go stores a
+    Note that this is a second, independent cache, stacked below the Docker
-    passing result in its cache directory (`GOCACHE`), and when the same tests
+    layer cache that [issue #26](https://git.eeqj.de/sneak/prompts/issues/26)
-    run again on unchanged code it prints that result, marked `(cached)`,
+    addresses. `CHECK_EPOCH` guarantees the `RUN make test` _step_ re-executes;
-    without running them. That matters on a developer's machine, where this
+    it does not guarantee `go test` inside that step does any work, because the
-    target runs and the directory lasts from one run to the next. The `test`
+    `GOCACHE` baked into earlier image layers survives into the re-executed
-    phase of the `Dockerfile` needs no `-count=1`: its base image holds no
+    step. They are two separate defects requiring two separate fixes, and a fix
-    result for this repo's tests and nothing before its `go test` step runs a
+    for one must not be recorded as covering the other.
-    test, so there is nothing to replay. `--no-cache` (above) is what makes that
-    step run on an unchanged tree.
 
     Python example:
 
@@ -642,6 +640,8 @@ style conventions are in separate documents:
     - JS: `package.json`, `yarn.lock`, `.prettierrc`, `.prettierignore`
     - Python: `pyproject.toml`
 
-- Guidance for coding agents lives in one `AGENTS.md` at the repository root. It
+- Guidance for coding agents lives in one `AGENTS.md` at the repository root,
-  is never committed under a file or directory named after one agent tool, such
+  including anything an agent should remember about the repo from one session to
-  as `CLAUDE.md` or `.claude/`, and never split into separate memory files.
+  the next. It is never committed under a file or directory named after one
+  agent tool, such as `CLAUDE.md` or `.claude/`, and never split into separate
+  memory files.