docs: task check is the check; the private mirrors on the profile

CONTRIBUTING.md

@@ -23,7 +23,7 @@ its own adds to them and says what it adds.
 ## Checking a change
 
 ```sh
-task render   # dry-run the whole pipeline inside the toolbox, no network
+task check    # render every command of the pipeline inside the toolbox, no network, and diff it against render.txt
 ```
 
 The check workflow runs the same render on every pull request and compares it with the

PULL_REQUEST_TEMPLATE.md

@@ -8,5 +8,5 @@
 
 ## Test plan
 
-- [ ] `task render` passes and the committed render was updated if the commands changed
+- [ ] `task check` passes, and `render.txt` was updated with `task render-update` if the commands changed
 - [ ] Verbs that write to a bucket were run on a fork against a scratch bucket, or this change touches none

SECURITY.md

@@ -26,7 +26,7 @@ This policy applies to every katoptra repository that has no SECURITY file of it
   account's token; a pull-request check gets no secret at all.
 
 Everything else on a public mirror is served as upstream serves it. Problems with the
-packages themselves belong upstream, to CTAN, TeX Live, CRAN or CPAN. This
+packages themselves belong upstream, to CTAN or TeX Live. This
 organization copies what they publish.
 
 ## Reporting

profile/README.md

@@ -2,41 +2,55 @@
 
 Greek for mirrors. Bytes here are closer than they appear.
 
-Each repository is one mirror: an upstream, a bucket, and a pipeline that syncs the two
-on a schedule from GitHub Actions. The mirrors are served from Cloudflare R2 and listed
-with live status at [katoptra.org](https://katoptra.org/).
+Each repository is one mirror: an upstream, a sink, and a pipeline that syncs the two on
+a schedule from GitHub Actions. The public mirrors are served from Cloudflare R2 and
+listed with live status at [katoptra.org](https://katoptra.org/).
 
 | Mirror | Upstream | Cadence | Repository |
 |---|---|---|---|
 | [ctan.katoptra.org](https://ctan.katoptra.org/) | [CTAN](https://ctan.org), all of it | hourly | [ctan](https://github.com/katoptra/ctan) |
 | [tlnet.katoptra.org](https://tlnet.katoptra.org/) | CTAN `systems/texlive/tlnet`, what `tlmgr` installs from | daily | [tlnet](https://github.com/katoptra/tlnet) |
 
+Two more mirror into Proton Drive rather than onto the web. What they copy is private;
+the pipelines are public and run on the same toolbox, so they are forks like the others.
+
+| Mirror | Upstream | Cadence | Repository |
+|---|---|---|---|
+| GitHub | every repository under the owners it names, one git bundle each | nightly | [github](https://github.com/katoptra/github) |
+| Dropbox | one Dropbox account | nightly | [dropbox](https://github.com/katoptra/dropbox) |
+
 More are on the way.
 
 ## Why this exists
 
 - I built these for myself. They live here so the pipelines are namespaced and share one
   toolbox.
-- Open source in the sense that you can fork and run it. Or just use these published
+- Open source in the sense that you can fork and run it. Or just use the published
   mirrors like I do.
 
 ## How a mirror runs
 
-- `list` the upstream, `diff` it against the `state` the last run left behind, then
-  `publish` the delta and `checkpoint` the state.
-- `verify` data and signatures whenever upstream provides them.
-- Works in batches, sized for a GitHub Actions runner.
-- Pings a healthcheck after each run if you give it one.
-- Keeps its state and checkpoints in R2 or any S3-compatible bucket. Cloudflare is the
-  default for its versatility and free egress.
-- I preferentially use 1Password for secrets, but GitHub secrets work too.
+- Everything the mirrors share lives once, in [lib](https://github.com/katoptra/lib):
+  the toolbox that starts a run, contains it in an image, resolves its secrets, checks
+  it and reports it, and an engine per transport that moves the bytes. lib's README is
+  the manual.
+- An rsync mirror lists upstream, diffs the listing against the state the last run left
+  in the bucket, publishes the delta in batches and checkpoints after each. It verifies
+  data and signatures wherever upstream provides them.
+- A Proton mirror stages what its upstream holds and uploads it in one call; unchanged
+  files are skipped, changed ones become revisions, and Proton's version history is the
+  history of the mirror.
+- Every run happens inside one pinned image, on a laptop and in Actions alike, and pings
+  a healthcheck when it finishes. Silence is the alert.
+- Secrets reach a run by name from a vault. No credential, account identifier, bucket
+  name or endpoint is in any repository.
 
 ## Want your own?
 
-- Fork a mirror.
-- Set three vars in its Taskfile: `SOURCE` (the upstream rsync URL), `BUCKET` (your
-  bucket name) and `HOST` (the domain in front of it).
-- Point the workflow at your vault, or your repository secret.
+- Fork a mirror and follow its README's "Want your own?": the lines to change, the
+  bucket, the vault item, its own accounts, the first run.
+- Everything the mirrors share, from making a vault and a service account to what the
+  bucket holds and how the workflows run, is in lib's README, once.
 - A full CTAN mirror costs under two dollars a month.
 
 ## Contributing