refactor: migrate package installation from pak to uvr (#147)

`bincraft` dropped pak in favour of uvr (5.0.x, "Dependencies and their system requirements are now installed with `uvr` instead of pak during `build_binary_package()`"), so the pipelines, helper scripts and images in this repo move with it.

## Approach

uvr is project-scoped in a way pak is not: `uvr add` refuses to run outside a project and always installs into `.uvr/library/`, and only `uvr sync` honours `--library`. So there is no one-line `pak::pak(...)` equivalent. `local/uvr-install.sh` encapsulates the dance — bootstrap a pinned uvr, mint a throwaway project under `TMPDIR`, `uvr add --no-install`, then `uvr sync --library <target>`. Keeping the project outside the checkout also keeps `uvr init`'s `.Rprofile` from hijacking `.libPaths()` for every other R call in the pipeline.

This matches what bincraft itself does (`uvr sync --install-system-deps --library <lib>`), and bincraft requires `uvr` on `PATH`, which the bootstrap provides: every pipeline that calls `bincraft::` runs `install-bincraft.R` (and therefore the bootstrap) first.

## Changes

| File | Change |
| --- | --- |
| `local/uvr-install.sh` | **New.** The single replacement for `pak::pak(...)`. Bootstraps uvr `v0.4.4`, resolves the R interpreter from `UVR_R_BIN`/`R_VERSION`/`PATH`, pins the manifest to that R's exact version, and syncs into `UVR_TARGET_LIB`/`R_LIBS_USER`. |
| `local/install-bincraft.R` | Installs `forgejo::codefloe.com/rpkgs/bincraft@<tag>` instead of a `git::` URL; keeps the `git ls-remote` tag resolution. Exports `UVR_R_BIN`/`UVR_TARGET_LIB` from `R.home()`/`.libPaths()[1]` so the per-R-minor passes target their own R and library. |
| `.crow/auto-apply-patches.yaml`, `.crow/weekly-patch-proposals.yaml`, `.crow/weekly-audit-missing.yaml`, `.crow/weekly-rebuild-missing.yaml`, `.crow/build-all-versions-install-deps.yaml` | `pak::pak(...)` → `UVR_R_BIN=/opt/R/$R_VERSION/bin/R local/uvr-install.sh ...`. The explicit `UVR_R_BIN` matters in `build-all-versions-install-deps.yaml`, which has no `R_VERSION` in its step environment. |
| `.crow/build-all-versions.yaml`, `.crow/process-updates.yaml`, `.crow/weekly-rebuild-missing.yaml` | `R_PKG_CACHE_DIR` → `UVR_CACHE_DIR` + `UVR_PACKAGES_DIR` on the same `/mnt/cache` volume, preserving the amd64-off/arm64-on split. Drops the `rm -rf .../pkgcache/_metadata/...` cleanup. |
| `local/r-minor-helpers.R`, `local/build-all.R`, `local/tests/test-trim-pkgcache.R` | Removes `trim_pkgcache_metadata()`, its every-25-packages call and its tests. uvr's cache does not mint a fresh ~70 MB snapshot per `PACKAGES` change. |
| `.crow/build-all-versions-install-deps.yaml` | Drops `pak::sysreqs_db_update()`; uvr resolves sysreqs from its vendored `r-system-requirements` rules via `--install-system-deps`. |
| `docker/Containerfile-shiny-app` | Bootstraps uvr and drives both dependency installs through one uvr project with `UVR_LIBRARY` pointed at the image's R library. |
| `docker/build-one.Dockerfile` | Ships `uvr-install.sh` at `/work/local/` so `install-bincraft.R` finds it. |
| `docker/reprex/alpine.sh` | Replaces `pak::local_install_deps()` with DESCRIPTION parsing + `uvr add`. |
| `local/test-package-loading.R` | Installs via the helper instead of `pak::pkg_install()`. |
| `README.md` | Documents uvr for sysreq inference, archived-version installs and cache clearing. |
| `renovate.json` | Tracks the `UVR_PIN` in `uvr-install.sh` via `github-releases`. |

## Behaviour notes

- **`weekly-audit-missing` still takes bincraft from the default branch**, not the latest release tag, matching what the `git::` pak call did. Called out in a comment rather than silently changed.
- **The uvr pin is repo-wide.** bincraft resolves `uvr` from `PATH` and pins no version of its own, so `UVR_PIN` in `uvr-install.sh` governs the whole pipeline.
- **Persistent caches now also benefit bincraft**, which reads `UVR_CACHE_DIR`/`UVR_PACKAGES_DIR` from the inherited pipeline environment.
- **`uvr sync` will not prune the shared library.** Pruning is disabled whenever `--library` is passed (`do_prune = prune && library_override.is_none()`), so `/mnt/cache/R-pkgs` keeps bincraft and its dependencies. The wipe-on-ABI-mismatch path is *not* similarly guarded, which is why the helper pins the manifest to the active R's exact version.
- **`plans/` and `specs/` are untouched** — they are dated records of decisions made in June 2026 and describe bincraft's then-pak-based internals; rewriting them would misstate history.

## Verification

`shellcheck`, all pre-commit hooks (on this commit's file range) and the `local/tests/` suite (100 assertions) pass.

Not yet exercised in CI: the build-env images do not ship `uvr`, so the per-step `curl install.sh` bootstrap is untested against a real image. Worth a manual `build-all-versions-install-deps` run before merging.

Reviewed-on: #147

.crow/weekly-rebuild-missing.yaml

@@ -141,7 +141,8 @@ steps:
       FORGEJO_TOKEN:
         from_secret: FORGEJO_TOKEN
       GIT_USER: pat-s
-      R_PKG_CACHE_DIR: /mnt/cache/pkgcache
+      UVR_CACHE_DIR: /mnt/cache/uvr/cache
+      UVR_PACKAGES_DIR: /mnt/cache/uvr/packages
       R_LIBS_USER: /mnt/cache/R-pkgs
       R_VERSION: ${R_VERSION}
       CCACHE_DIR: /mnt/cache/ccache
@@ -150,12 +151,12 @@ steps:
       NCPUS: 2
     commands:
       - git clone -q https://pat-s:$$REPO_RO_TOKEN@git.devxy.io/devxy/build-cran-binaries.git .
-      - mkdir -p /mnt/cache/pkgcache /mnt/cache/R-pkgs /mnt/cache/ccache /mnt/cache/packages
+      - mkdir -p /mnt/cache/uvr/cache /mnt/cache/uvr/packages /mnt/cache/R-pkgs /mnt/cache/ccache /mnt/cache/packages
       - rm -rf /mnt/cache/R-pkgs/00LOCK-*
       - /opt/R/$R_VERSION/bin/Rscript local/install-bincraft.R
       - /opt/R/$R_VERSION/bin/R -q -e 'packageVersion("bincraft")'
       - XVFB=$(command -v xwfb-run 2>/dev/null || command -v xvfb-run); XVFB_ARGS=""; if command -v xwfb-run >/dev/null 2>&1; then dnf install -y -q weston 2>/dev/null; XVFB_ARGS="-c weston"; fi
-      - /opt/R/$R_VERSION/bin/R -q -e 'pak::pak("httr2")'
+      - UVR_R_BIN=/opt/R/$R_VERSION/bin/R local/uvr-install.sh httr2
       - /opt/R/$R_VERSION/bin/R -q -e 'source("local/fetch-rebuild-packages-from-issue.R")'
       - $XVFB $XVFB_ARGS -- /opt/R/$R_VERSION/bin/R -q -e "sink(stdout(), type = 'message'); options(crayon.enabled = TRUE, Ncpus = $NCPUS, future.globals.onReference = NULL); pkgs <- readLines('/tmp/rebuild_pkgs.txt'); if (length(pkgs) == 0) { cat('Nothing to rebuild\n'); q('no') }; excluded <- jsonlite::fromJSON('local/excluded-packages.json')[['package']]; pkgs <- setdiff(pkgs, excluded); cat(sprintf('Rebuilding %d packages\n', length(pkgs))); n <- length(pkgs); for (i in seq_along(pkgs)) { x <- pkgs[i]; cat(sprintf('[%d/%d] %s\n', i, n, x)); tryCatch(bincraft::build_binary_package(x, tag_limit = 1L, patches = 'local/patches', s3_endpoint = 'https://s3.eu-central-003.backblazeb2.com', s3_region = 'eu-central-003', s3_bucket = 'devxy-rpkgs-binaries', s3_access_key_id = Sys.getenv('B2_S3_ACCESS_KEY'), s3_secret_access_key = Sys.getenv('B2_S3_SECRET_KEY'), metadata_db_host = 'r-binaries.devxy.io', metadata_db_name = 'build_metadata', metadata_db_table = 'single_builds', metadata_db_user = 'rpkgs', metadata_db_password = Sys.getenv('PGPASS'), metadata_db_sslmode = 'require', metadata_db_port = 15432, archive = TRUE, upload = TRUE, store_build_metadata = TRUE), error = function(e) cat(sprintf('ERROR building %s - %s\n', x, conditionMessage(e)))) }" 2>&1
     backend_options: