refactor(ci): consolidate per-platform crow workflows into 3 matrix files (#92)

## Summary

Collapse **44** per-platform crow pipeline files into **3** matrix-driven files (one per family), using `matrix.include` + the crow #1165 declarative manual `variables:` block:

| Family | Before | After |
|---|---|---|
| process-updates | 14 | `process-updates.yaml` |
| weekly-audit-missing | 16 | `weekly-audit-missing.yaml` |
| weekly-rebuild-missing | 14 | `weekly-rebuild-missing.yaml` |

- **One file per family** (not split by arch). Arch placement is via the agent label as a matrix var (`artemis`=amd64, `gaia`=arm64) for process-updates and weekly-rebuild; weekly-audit keeps its arch-`nodeSelector` placement (no agent label).
- **Matrix axis is named `OS`** (e.g. `redhat-9`) per request, with per-row `R_VERSION`, image tag, codename, and `process_new` (FALSE for alpine).
- **Runs preserved 1:1:**
  - *Cron*: each existing `<family>-<os>-<arch>` cron still fires only its matching matrix row via `CI_PIPELINE_CRON`. Server-side cron entries unchanged.
  - *Manual*: a #1165 dropdown variable (`process_cran_updates` / `weekly_audit_missing` / `weekly_rebuild_missing`) selects a single `<os>-<arch>` or `all`. weekly-rebuild defaults to `all`, matching its former bare `event: manual` trigger.

## Behavior deltas (intentional, flagged)

To fit one file per family the backend was unified:
- The amd64-only `node.kubernetes.io/instance-type: AX42` nodeSelector pin is **dropped**; placement now relies on the `artemis`/`gaia` agents.
- **process-updates arm64** jobs now share the same `backend_options` as amd64 (resource requests/limits + tolerations) — they previously had none, so they gain an 18Gi memory limit. Tell me if arm64 should stay uncapped.

## Validation required before merge

Relies on crow interpolating matrix variables inside `when.evaluate`, `labels.agent`, and `commands`. Interpolation in image/env/commands is standard crow; the novel bit is `when.evaluate`. The manual dropdown routing exercises the same interpolation as the cron routing, so on this branch:
1. Trigger manually with the dropdown = `redhat-9-amd64` -> confirm only that one job runs (image `build-env-redhat:9`, R 4.4.3, agent artemis).
2. Trigger with `all` -> confirm all os/arch jobs schedule.

Crons only fire on the default branch, so no collision while unmerged. Fallback if `${...}` doesn't interpolate in `when`: a runtime `case "$CI_PIPELINE_CRON" in ...` guard, same files otherwise.

Reviewed-on: #92

.crow/weekly-rebuild-missing-alpine-322-arm64.yaml

@@ -1,63 +0,0 @@
-when:
-  - event: cron
-    cron: weekly-rebuild-missing-alpine-322-arm64
-  - event: manual
-
-skip_clone: true
-
-labels:
-  agent: gaia
-
-steps:
-  - name: 'Rebuild missing binaries'
-    image: reg.devxy.io/rpkgs/build-env-alpine:3.24
-    pull: true
-    environment:
-      RED_HAT_DEV_PW:
-        from_secret: RED_HAT_DEV_PW
-      B2_S3_ACCESS_KEY:
-        from_secret: B2_S3_ACCESS_KEY
-      B2_S3_SECRET_KEY:
-        from_secret: B2_S3_SECRET_KEY
-      PGPASS:
-        from_secret: PGPASS
-      REPO_RO_TOKEN:
-        from_secret: REPO_RO_TOKEN
-      GITHUB_PAT:
-        from_secret: GITHUB_PAT
-      FORGEJO_TOKEN:
-        from_secret: FORGEJO_TOKEN
-      GIT_USER: pat-s
-      R_PKG_CACHE_DIR: /mnt/cache/pkgcache
-      R_LIBS_USER: /mnt/cache/R-pkgs
-      R_VERSION: 4.5.3
-      CCACHE_DIR: /mnt/cache/ccache
-      PLATFORM: alpine-322
-      ARCH: arm64
-      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
-      - rm -rf /mnt/cache/R-pkgs/00LOCK-*
-      - /opt/R/$R_VERSION/bin/R -q -e 'if (!requireNamespace("bincraft", quietly = TRUE) || packageVersion("bincraft") != "4.2.2") pak::pak("git::https://codefloe.com/rpkgs/bincraft.git@v4.2.2")'
-      - /opt/R/$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")'
-      - /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, 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:
-      kubernetes:
-        resources:
-          requests:
-            memory: 5Gi
-            cpu: 3000m
-          limits:
-            memory: 18Gi
-            cpu: 3000m
-        nodeSelector:
-          kubernetes.io/arch: arm64
-        tolerations:
-          - key: 'CI'
-            operator: 'Equal'
-            value: 'true'
-            effect: 'NoSchedule'