MIL-008: plan the wiki as a reusable workflow, ADR-0009, RC-060, RC-061

MIL-008 plans publishing the wiki through a reusable workflow that reads
docs/wiki/. ADR-0009 records the decision. RC-060 accepts the plan; RC-061
accepts the amendment that deprecates the scoped workflow instead of
removing it, because eight repositories still publish through it.

docs/adr/adr-0009-wiki-publishing-reusable-workflow.md

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+# ADR-0009: Wiki publishing as a reusable workflow
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | ADR-0009 |
+| CrossReference | [MIL-008], [ADR-0003], [ADR-0004], [ADR-0005], [ADR-0006] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-13 | Proposed | Jens Tirsvad Nielsen | S01 | Initial version | pending |
+
+Allowed Status values: `Proposed`, `Accepted`, `Rejected`, `Deprecated`, `Superseded by ADR-NNNN`.
+
+---
+
+## Context
+
+[ADR-0004] chose a scoped workflow to publish wikis: Gitea runs it in every
+repository of an organisation, and a marker file `wiki/.publish` is the opt-in.
+That avoids a copy of the workflow, but it runs where nobody asked for it and
+needs a safety gate for that reason; its trigger path (`wiki/**`) and the
+version of the script (`v1`) are fixed centrally. The framework now prescribes
+the wiki in `docs/wiki/` with English and the PO language as a minimum, and
+repositories need to say where their wiki is.
+
+Options:
+
+1. **Keep the scoped workflow and read both folders.** No file in consumers,
+   but the central trigger lists every location and the gate stays.
+2. **A reusable workflow (`workflow_call`) that each repository calls.** One
+   source in this repository, called as `uses: ...@v1` the way
+   `quality-checks` and `release` already are ([ADR-0005], [ADR-0006]). The
+   caller sets its own trigger paths and the folder.
+
+## Decision
+
+Wiki publishing is the reusable workflow `publish-wiki-pages.yml`, called by
+each repository that wants a published wiki; the caller file is the opt-in and
+`docs/wiki/` is the default folder. The scoped `publish-wiki.yml` and the
+`wiki/.publish` marker are deprecated and stay until every publishing repository
+has a caller; they are then removed in a later major release.
+
+The rules that follow from it:
+
+- Inputs: `wiki_dir` (default `docs/wiki`), `prune` (default `false`) and
+  `tools-ref` (default `v1`). The secret `TOKEN_FOR_GITEA_WIKI` is declared and
+  passed by the caller; there is no fallback to another token.
+- With the reusable workflow the marker is not read: the script treats the
+  `prune` input as the setting, and a missing folder is a configuration error
+  rather than a skip, because the caller asked for it.
+- The script, the page-title rules, the empty-folder protection and the error
+  categories of [ADR-0004] and [ADR-0003] are unchanged.
+
+## Consequences
+
+**Positive:**
+
+- A repository states its own folder and trigger paths, so the wiki can move
+  to `docs/wiki/` one repository at a time.
+- Opting in is a file in the repository, reviewed in a pull request, and a
+  repository without a caller is never written to.
+- One call convention for every shared workflow of this repository.
+
+**Negative:**
+
+- Every publishing repository needs a caller file, and the removal of the
+  scoped workflow stops publishing in any repository that still relies on the
+  marker; the list of those repositories is taken before the removal.
+- Eight repositories still publish through the scoped workflow (checked on
+  2026-10-13), so it is deprecated and not removed here; removing it is a
+  breaking change under [ADR-0006] and belongs to a follow-up milestone with
+  their migrations.
+- The owner chose a patch release (1.2.2) for this change although a new
+  workflow is a minor one under [ADR-0006]; the changelog states the deviation.
+- Passing a declared secret through `workflow_call` is not yet verified on this
+  Gitea instance; it is checked by the first call, in this repository.
+
+## Affected Artifacts
+
+- [MIL-008] — the plan this decision belongs to.
+- [ADR-0004] — its scoped delivery and marker parts are replaced once the
+  scoped workflow is removed; its token and safety rules stand.
+
+---
+
+[MIL-008]: ../milestones/mil-008-wiki-reusable-workflow.md
+[ADR-0003]: ./adr-0003-wiki-publish-token.md
+[ADR-0004]: ./adr-0004-shared-wiki-publishing-opt-in.md
+[ADR-0006]: ./adr-0006-release-process-and-version-pinning.md
+[ADR-0005]: ./adr-0005-quality-check-contract.md