test: backfill raw/global/computed report triplet coverage across plugins

The bats coverage for plugin :report keys has been uneven since the raw/global/computed split landed in PR #8640. This commit adds a single combined triplet test per settable property across app-json, builder, builder-dockerfile, builder-herokuish, builder-lambda, builder-nixpacks, builder-pack, builder-railpack, buildpacks, cron (maintenance), git (keep-git-dir, rev-env-var, source-image), logs (vector-sink, vector-global-image, vector-global-networks), network (attach-post-create, attach-post-deploy, initial-network), proxy (per-app type), ps (stop-timeout-seconds), registry (image-repo, push-on-release, push-extra-tags), storage (build/deploy/run mounts), and adds a new tests/unit/scheduler.bats and tests/unit/nginx-vhosts_properties.bats. Brings ps `procfile-path` and `stop-timeout-seconds` global getters in line with the #8640 convention (raw global, default resolved in computed). Documents the read-only and internal properties that surface in `:report` (or are written by Dokku) but cannot be managed by `:set` in a new `## Internal properties` section appended to each affected plugin's docs page.

docs/processes/process-management.md

@@ -463,3 +463,12 @@ The default value (`true`) may be restored by passing an empty value:
 ```shell
 dokku ps:set node-js-app restore
 ```
+
+## Internal properties
+
+The following properties surface in `ps:report` but are not managed by `ps:set` - they are derived from the running process state:
+
+| Property | Kind | Description | Source |
+|---|---|---|---|
+| `--ps-can-scale` | read-only | `false` when the app's procfile or builder forbids horizontal scaling | derived from procfile parse |
+| `--deployed`, `--running`, `--processes`, `--status-<proctype>` | read-only | Live process state | `plugins/ps/report.go` inspects running containers |