Set a time limit on the canonical check job (closes #120)

The canonical check workflow gave its job no time limit, so a hung
script/cibuild held the shared runner until the runner's own default.
The check job now sets timeout-minutes: 20. script/cibuild runs three
Docker builds (the test phase, the lint phase, then the image, which
runs both again), each held to the 5-minute build limit, plus the
bootstrap. REPO_POLICIES.md and both checklists name the limit among
what the workflow sets.

Model: opus-5-5

TODO.md

@@ -29,6 +29,10 @@ fmt-check, and commit.
   follows it. `REPO_POLICIES.md` and both checklists name the limit among what
   the workflow sets. Not yet tried on the shared runner. Repositories pick this
   up on their next re-vendor.
+- 2026-10-07: The canonical `package.json` now has `"private": true` in place of
+  `"license": "MIT"` (issue 119), so a repository that copies it no longer
+  declares MIT whatever its own licence is. yarn does not print "No license
+  field" for a private package. This repository's own licence is unchanged.
 - 2026-10-06: The canonical `.gitea/workflows/check.yml` now sets
   `fetch-depth: 0` on its checkout step (issue 110), so CI fetches the history
   and tags that `git describe --tags --always` needs, and a tagged repository

package.json

@@ -1,5 +1,5 @@
 {
-  "license": "MIT",
+  "private": true,
   "devDependencies": {
     "prettier": "3.8.1"
   }

prompts/REPO_POLICIES.md

@@ -298,21 +298,20 @@ style conventions are in separate documents:
   workflow's `concurrency` block groups runs by workflow and branch
   (`${{ github.workflow }}-${{ github.ref }}`) with `cancel-in-progress: true`,
   so a new push cancels the older run on the same branch, queued or running, and
-  no other: runs for replaced commits do not hold up the shared runner. The
-  `check` job sets `timeout-minutes: 20`, so a hung build frees the shared
-  runner after 20 minutes. That allows for the three Docker builds
-  `script/cibuild` runs (the lint phase, the test phase, then the image, which
-  runs both again), each held to the 5-minute Docker build limit below, plus the
-  bootstrap. `script/cibuild` bootstraps, runs the gate phases, and then builds
-  the image, so a successful run means every check passed; a bare
-  `docker build .` does not carry the same guarantee, because its gate phases
-  may come from the cache. The image build is uncached and so runs the gate
-  phases a second time. That is the price of the rule above, and it is worth
-  paying: the image that ships is built from a run of its own gates rather than
-  from a cache entry. A separate workflow limited to `main` by a `branches` list
-  under `on: push` cannot be checked by review: to try a change to it, add the
-  feature branch to that list and push, then remove the branch from the list
-  again before merging. Keep any job in it that publishes behind
+  no other: runs for replaced commits do not hold up the shared runner.
+  `script/cibuild` bootstraps, runs the gate phases, and then builds the image,
+  so a successful run means every check passed; a bare `docker build .` does not
+  carry the same guarantee, because its gate phases may come from the cache. The
+  image build is uncached and so runs the gate phases a second time. That is the
+  price of the rule above, and it is worth paying: the image that ships is built
+  from a run of its own gates rather than from a cache entry. The `check` job
+  sets `timeout-minutes: 20`, so a hung build frees the shared runner after 20
+  minutes. That allows for the three Docker builds described above (the test
+  phase, the lint phase, then the image), each held to the 5-minute Docker build
+  limit below, plus the bootstrap. A separate workflow limited to `main` by a
+  `branches` list under `on: push` cannot be checked by review: to try a change
+  to it, add the feature branch to that list and push, then remove the branch
+  from the list again before merging. Keep any job in it that publishes behind
   `if: github.ref_name == 'main'`, so the run from the feature branch publishes
   nothing.