feat(drupal-core): switch to amateescu/ddev-drupal-dev scaffolding, fixes #142

[rfay]

Summary

• Replaces `joachim-n/drupal-core-development-project` (composer create-project) with a direct `git clone` of `drupal/drupal` + the `amateescu/ddev-drupal-dev` DDEV add-on
• Eliminates ~440 lines of bash: inline-alias JSON fixups, json-schema pin, vendor symlink restoration, and branch-aware `composer update -W` are gone — the add-on's `composer.local.json` overlay keeps core's `composer.json` untouched
• Drush is added via `ddev composer require drush/drush` into `composer.local.json`
• Issue forks still work: `git remote add issue` + fetch + checkout before `ddev composer install`
• Non-main branches (10.x, 11.x) work via plain `git checkout` — no composer.json fixups needed
• Old joachim-n workspaces are detected on restart and kept as-is (with a note to recreate to migrate); docroot auto-detects old vs new scaffolding
• `cache_path` is now optional (`default = ""`); used as a `git --reference` hint with silent fallback to a direct clone if the cache seed is missing or broken
• Welcome message and `ddev launch` command now document `ddev add-module`, `ddev phpunit`, and link to https://github.com/amateescu/ddev-drupal-dev

Cache seed — required admin action on both servers

The cache structure has changed. The seed is now a plain git clone at the root of the seed directory (no `repos/drupal/` nesting). The startup script checks for `.git` at the seed root and uses it as a `git --reference` hint.

The old `repos/drupal/` structure is not detected — new workspaces will fall back to a direct clone (slower) until the cache is migrated.

Run these steps on each server:

SEED_DIR=~/cache/drupal-core-seed
REPO=~/workspace/coder-ddev

# 1. Stop the old DDEV seed project
cd "$SEED_DIR" && ddev stop --remove-data 2>/dev/null || true

# 2. Move the git clone to the seed root, remove everything else
mv "$SEED_DIR/repos/drupal" /tmp/drupal-git-tmp
rm -rf "$SEED_DIR"
mv /tmp/drupal-git-tmp "$SEED_DIR"

# 3. Install the updated update script and service
sudo install -m 755 $REPO/drupal-core/scripts/update-drupal-cache   /usr/local/bin/update-drupal-cache
sudo install -m 644 $REPO/drupal-core/scripts/drupal-cache-updater.service   /etc/systemd/system/
sudo systemctl daemon-reload

# 4. Verify it works
sudo systemctl start drupal-cache-updater.service
journalctl -u drupal-cache-updater.service --no-pager | tail -10

After migration, `~/cache/drupal-core-seed` is the git clone itself — `.git` at the root. The updated `update-drupal-cache` script runs `git fetch --all --prune` instead of `ddev composer update`.

Full instructions (including fresh setup for new servers) are in `docs/admin/server-setup.md` Step 10.

Closes #142

Test plan

• `terraform fmt -recursive` passes
• `terraform -chdir=drupal-core validate` passes
• CI Terraform mock unit tests pass (require Terraform ≥ 1.6)
• Create a new workspace with default parameters (Drupal 12/main) — Drupal installs and site is accessible
• Create a workspace with an issue fork number and branch — correct branch checked out, Drupal installs
• Create a workspace with Drupal 11 selected — 11.x branch checked out, Drupal installs
• Restart an existing old-scaffolding workspace — detects old structure, logs warning, continues working
• `ddev add-module token` works inside a new workspace
• `ddev phpunit core/modules/node` works inside a new workspace
• Run migration steps on both servers; verify `drupal-cache-updater.timer` fires and `git fetch` completes cleanly

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