songs: replace the wiki.siblings macro with plain Markdown links

The `wiki.siblings` bill of materials is gone. A related co-publication is
now nominated with an ordinary relative Markdown link — `[label](notes.md)` —
resolved at publish time against the target file's own `title` frontmatter.
No macro namespace, no per-file declaration, and the link still works in
Gitea's blob view and any editor preview.

The macro could not be made safe. Substitution was `str.replace(tag, …)` over
the whole rendered page: no word boundary, so a tag also occurring in lyrics or
a code block got rewritten; no collision check, so overlapping tags corrupted
each other in declaration order. SCHEMA.md documented the placeholder as
`[[TAG]]` while the code replaced the bare tag, so following the schema
produced `[[[[Title|label]]]]`.

Fixes a live corruption bug in the process. `sibling_map` was built only from
the files in the publish batch, and an unresolved sibling degraded to plain
text — so pushing `ses/pulse.md` alone republished it with its wikilink
silently stripped to the bare words "Dev gibberish". SCHEMA.md asserted the
workflow "always runs --all", which it never did on an ordinary push.

The repository is now always scanned in full, whatever a run publishes, so
link resolution and title-collision detection can never depend on which files
a push touched. Writes stay bounded to the push diff plus one hop in each link
direction: the page a changed page links to (so a link cannot point at an
unpublished page) and the pages linking to it (so an edited `title` does not
leave stale inbound links). Publishing is not instant; reading is cheap.

An unresolvable `.md` link is now a hard error, never graceful degradation, and
linking to a file still does not publish it — `wiki.publish: true` remains the
only gate. A leftover-link guard fails the run on any link shape the resolver
did not recognise, including a Markdown link written inside a verbatim
```columns fence, so a pandoc upgrade cannot silently publish literal text.

Also:

- render before write: every page in a run is rendered before the first is
  published, so a broken page leaves the wiki untouched instead of
  half-updated. `publish_one` is split into `render_page` (pure) and the write.
- pin pandoc's stdout to UTF-8. `text=True` decoded it with the ambient locale
  encoding; on any non-UTF-8 locale the Japanese and Chinese lyrics died inside
  subprocess's reader thread, `stdout` came back None, and the real error was
  lost behind a TypeError. Latent on the Debian runner via PEP 538 only.
- title collisions are detected repo-wide, not just within a push, and before
  any wiki contact.
- tests/, run by .gitea/workflows/test.yml in the publish runner image. The
  pandoc output contract the resolver depends on is now pinned by a test
  instead of by prose — which is how SCHEMA.md came to assert something false.
- drop an f-string with nothing to interpolate.
- quote the SOURCE_REF interpolation in the workflow instead of pasting an
  input straight into shell.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/publish-songs.yml

@@ -6,14 +6,9 @@ on:
         required: true
         type: string
       SOURCE_BASE_REF:
-        description: "Commit SHA before the push (all-zeros = first push)"
+        description: "Commit SHA before the push (empty or all-zeros = first push)"
         required: true
         type: string
-      FULL_PUBLISH:
-        description: "Re-publish every file regardless of diff"
-        required: false
-        type: boolean
-        default: false
 
 jobs:
   publish:
@@ -26,9 +21,10 @@ jobs:
         env:
           FAPAT: ${{ secrets.FAPAT }}
           URL_TO_GITEA: ${{ vars.URL_TO_GITEA }}
+          SOURCE_REF: ${{ inputs.SOURCE_REF }}
         run: |
           git clone "http://mikkeli:${FAPAT}@${URL_TO_GITEA#http://}/novoyuuparosk-wiki/ncmr-songs" ncmr-songs
-          git -C ncmr-songs checkout ${{ inputs.SOURCE_REF }}
+          git -C ncmr-songs checkout "$SOURCE_REF"
 
       - name: Checkout auto-wiki
         env:
@@ -36,24 +32,28 @@ jobs:
           URL_TO_GITEA: ${{ vars.URL_TO_GITEA }}
         run: git clone "http://mikkeli:${FAPAT}@${URL_TO_GITEA#http://}/novoyuuparosk-wiki/novoyuuparosk-auto-wiki" auto-wiki
 
+      # The diff bounds what gets *written*, not what gets *read*. The publisher
+      # always scans the whole repository to resolve links and page titles, then
+      # writes only these files (plus, one hop out, any page they link to or that
+      # links to them). Passing a subset here is safe for that reason and only
+      # that reason — resolution no longer depends on the batch.
       - name: Detect changed files
         id: diff
+        env:
+          BASE: ${{ inputs.SOURCE_BASE_REF }}
+          HEAD: ${{ inputs.SOURCE_REF }}
         run: |
-          BASE="${{ inputs.SOURCE_BASE_REF }}"
-          HEAD="${{ inputs.SOURCE_REF }}"
-          # All-zeros base means first push — publish everything
+          # Empty or all-zeros base means first push or manual dispatch — publish everything
           if [ -z "$BASE" ] || echo "$BASE" | grep -qE '^0+$'; then
+            echo "First push or manual dispatch — publishing everything."
             echo "mode=all" >> "$GITHUB_OUTPUT"
-          else
-            git -C ncmr-songs diff --name-only "$BASE" "$HEAD" -- '*.md' \
-              | grep -v '^wip/' \
-              | grep -v '^README\.md' \
-              > /tmp/changed.txt 2>/dev/null || true
-            echo "Changed files:"
-            cat /tmp/changed.txt
-            echo "mode=incremental" >> "$GITHUB_OUTPUT"
-            echo "files=$(tr '\n' ' ' < /tmp/changed.txt)" >> "$GITHUB_OUTPUT"
+            exit 0
           fi
+          CHANGED=$(git -C ncmr-songs diff --name-only "$BASE" "$HEAD" -- '*.md' | grep -v '^wip/' || true)
+          echo "Changed files:"
+          echo "$CHANGED"
+          echo "mode=incremental" >> "$GITHUB_OUTPUT"
+          echo "files=$(echo "$CHANGED" | tr '\n' ' ')" >> "$GITHUB_OUTPUT"
 
       - name: Publish
         env:
@@ -63,20 +63,14 @@ jobs:
           WIKI_BOT_PASSWORD: ${{ secrets.WIKI_BOT_PASSWORD }}
           SOURCE_REF: ${{ inputs.SOURCE_REF }}
           GITEA_REPO_URL: ${{ vars.URL_TO_GITEA }}/novoyuuparosk-wiki/ncmr-songs
+          MODE: ${{ steps.diff.outputs.mode }}
+          FILES: ${{ steps.diff.outputs.files }}
         run: |
-          MODE="${{ steps.diff.outputs.mode }}"
-          if [ "$MODE" = "all" ] || [ "${{ inputs.FULL_PUBLISH }}" = "true" ]; then
-            python auto-wiki/pipelines/songs/publish.py \
-              --source-dir ncmr-songs \
-              --all
-          else
-            FILES="${{ steps.diff.outputs.files }}"
-            if [ -z "$FILES" ]; then
-              echo "No changed .md files detected. Nothing to publish."
-              exit 0
-            fi
+          if [ "$MODE" = "all" ]; then
+            python auto-wiki/pipelines/songs/publish.py --source-dir ncmr-songs --all
+          elif [ -n "$(echo "$FILES" | tr -d '[:space:]')" ]; then
             # shellcheck disable=SC2086
-            python auto-wiki/pipelines/songs/publish.py \
-              --source-dir ncmr-songs \
-              --files $FILES
+            python auto-wiki/pipelines/songs/publish.py --source-dir ncmr-songs --files $FILES
+          else
+            echo "No changed .md files outside wip/. Nothing to publish."
           fi