fix(add-page-by-form): patch Grav-2.0 edit-mode header fatal + deploy wiring

Adding a new photo while editing an entry 500s: add-page-by-form's edit branch
reads existing frontmatter via `(array)$page->header()`, but Grav 2.0's
Grav\Common\Page\Header keeps data in a protected `items`, so the cast mangles
keys and `$original_frontmatter['photos']` is never set → array_merge(null,…)
TypeError. Fix: use Header::toArray() (clean keys, stdClass fallback) + guard the
per-field merge. Grav 2.0.7 does not change this — only the plugin fix does.

add-page-by-form is abandoned upstream (last release 2023-09) and its dir is
git-ignored/GPM-managed, so the fix is tracked as deploy/patches/*.patch and
re-applied after any GPM install/update:
- make apply-plugin-patches (local) — chained into install-plugins
- make remote-apply-plugin-patches-{test,prod} — piped over SSH into
  `patch -p1 --forward`; chained into remote-install-plugins / remote-update-plugins
Content syncs don't touch user/plugins/, so the patch survives them; only a GPM
op wipes it (now auto-restored). Runbook + README document the step and a
verify check. Remove once the plugin is forked.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/guides/deploy-cycle.md

@@ -64,18 +64,20 @@ Referenced gotcha docs:
 ```
 make remote-fetch-content-test              # 1. clean-reset synced folders to repo state
 make remote-upgrade-grav-test               # 2. gpm self-upgrade (rewrites schema — expect drift)
-make remote-update-plugins-test             # 3. gpm update the plugins.txt set
+make remote-update-plugins-test             # 3. gpm update the plugins.txt set (auto-applies deploy/patches/)
 make remote-gpm-install-test PKG=git-sync   # 4. EXPLICITLY (re)install each remote-only plugin
 make remote-apply-env-test                  # 5. re-deploy the env override (not synced; gone after install)
 ```
 
 Why each matters:
+- **Step 3** re-applies `deploy/patches/*.patch` automatically (it chains `remote-apply-plugin-patches`). GPM install/update lays down **pristine** third-party plugins, wiping local fixes to git-ignored `user/plugins/` — the patch step restores them. Content pulls (step 1) do **not** touch `plugins/`, so the patch only needs re-applying after a GPM op, not after every sync. Run `make remote-apply-plugin-patches-test` standalone if you ever GPM-install outside this sequence. Requires the `patch` tool on the server. See `deploy/patches/README.md`.
 - **Step 4** is non-optional even if git-sync "was already there" — remote-only plugins are not in `plugins.txt`, so nothing in steps 1–3 restores them. If the code is missing, the plugin is inert despite valid config.
 - **Step 5** re-writes `user/env/<host>/config/…` from `deploy/env/<env>/`. The env tree is not synced by anything, so a fresh install loses it until you re-apply.
 
 ### Verify (smoke checklist — this is the payoff)
 
 - **Code present, not just config:** `ls user/plugins/<name>/` for every expected plugin (especially `git-sync`). An empty/absent dir = reinstall (step 4). *(Do this via an ssh one-liner you run, or `make remote-diag-test`.)*
+- **Plugin patches applied:** confirm the add-page-by-form fix survived the GPM op — `grep -c toArray user/plugins/add-page-by-form/add-page-by-form.php` should be ≥1 (0 = pristine, re-run `make remote-apply-plugin-patches-test`). Functional check: edit a journal entry and add a photo — a pristine plugin 500s on save.
 - **HTTP:** `/` → 200, `/admin` → 200, `/api/v1/pages` → 401, `/gpx-manager` → 200. Watch for the double-`Content-Encoding` garbage page (fix: `debugger.shutdown.close_connection: false` in the env override — already in `deploy/env/prod/system.yaml`).
 - **Post smoke test:** submit one entry via `/post` and confirm it appears in the trip feed immediately. This proves the `cache-on-save` plugin works with prod caching on.
 - **Config drift:** `make remote-diag-test` — diff server config against the repo. Fold any *intended* schema migration (e.g. the Twig-3 `strict_mode` flags a `self-upgrade` writes) back into `user/config/system.yaml`, or the next `fetch-content` reverts it.