feat: unified drafts/ structure with PDF outputs for ACT and ECT

Both drafts now live in workspace/drafts/ as siblings:
  drafts/
  ├── act/                       (ACT -01, native to parent repo)
  │   ├── draft-nennemann-act-01.md     kramdown-rfc source
  │   ├── draft-nennemann-act-01.{xml,txt,html,pdf}
  │   ├── .refcache/             bibxml cache
  │   └── build.sh
  ├── ietf-wimse-ect/            (ECT -02, submodule, PDF added)
  │   └── ...
  └── README-pdf.md              PDF toolchain docs

ACT kramdown-rfc conversion:
- full YAML frontmatter (title, author, refs)
- section structure matches kramdown-rfc conventions
- {{REF}} citation syntax, auto-numbered sections
- references auto-built from normative/informative blocks
- removed manual TOC (kramdown-rfc generates)
- builds cleanly: 133K XML, 89K TXT, 208K HTML, 167K PDF

PDF toolchain:
- xml2rfc --pdf via weasyprint<60 + pydyf<0.10 injected into xml2rfc pipx venv
- both build.sh scripts now produce PDF as Step 4
- README-pdf.md documents the setup for new machines

Submodule: bump ietf-wimse-ect pointer for build.sh PDF step

workspace/drafts/README-pdf.md

@@ -0,0 +1,67 @@
+# PDF Generation for IETF Drafts
+
+## Status
+
+`xml2rfc --pdf` is wired up on this machine. PDFs are generated automatically
+as part of `build.sh` in each draft directory.
+
+## How it works
+
+`xml2rfc` is installed via `pipx` in its own venv
+(`/home/c/.local/share/pipx/venvs/xml2rfc/`). The `--pdf` switch requires
+several extra dependencies that had to be injected into that venv:
+
+```bash
+pipx inject xml2rfc "weasyprint<60" pycairo pangocffi
+/home/c/.local/share/pipx/venvs/xml2rfc/bin/python -m pip install "pydyf<0.10"
+```
+
+Version pins matter:
+- `weasyprint 59.x` — xml2rfc's `--pdf` code path calls weasyprint's
+  `write_pdf(target, stylesheets=[...], presentational_hints=True)`.
+  Newer weasyprint (60+) changes the signature.
+- `pydyf <0.10` — weasyprint 59 calls `pydyf.PDF(version, identifier)` with
+  two positional args. pydyf 0.10+ removed those.
+
+System libs used via ctypes: `pango`, `pangocairo`, `cairo`, `harfbuzz`
+(all already present via Fedora packages).
+
+Fonts: xml2rfc uses Noto + Roboto Mono embedded in the weasyprint output.
+Not installed system-wide but weasyprint fonttools handles them.
+
+## Build step (pattern for build.sh)
+
+After the HTML step, add:
+
+```bash
+# Step 4: XML -> PDF
+echo "Generating PDF output..."
+if "$XML2RFC" "$DIR/$DRAFT.xml" --pdf --quiet 2>/dev/null; then
+  PDF_OK=1
+else
+  echo "  xml2rfc --pdf failed; falling back to weasyprint on HTML"
+  if command -v weasyprint >/dev/null 2>&1; then
+    weasyprint "$DIR/$DRAFT.html" "$DIR/$DRAFT.pdf" >/dev/null 2>&1 \
+      && PDF_OK=1 || PDF_OK=0
+  else
+    PDF_OK=0
+  fi
+fi
+```
+
+## Verification
+
+`ietf-wimse-ect/draft-nennemann-wimse-ect-02.pdf` — 178 KB, generated via
+`xml2rfc --pdf` (IETF-idiomatic layout with Noto fonts, title page,
+bookmarks, and proper TOC). The fallback `weasyprint html->pdf` produces a
+172 KB PDF that works but renders the html2rfc template instead of the
+official IETF print layout; use it only if xml2rfc --pdf is unavailable.
+
+## Reinstallation checklist (on a new machine)
+
+1. `pipx install xml2rfc`
+2. `pipx inject xml2rfc "weasyprint<60" pycairo pangocffi`
+3. `/home/c/.local/share/pipx/venvs/xml2rfc/bin/python -m pip install "pydyf<0.10"`
+4. Install system libs: `dnf install pango cairo harfbuzz` (Fedora) or
+   `apt install libpango-1.0-0 libpangoft2-1.0-0 libharfbuzz0b` (Debian)
+5. Test: `xml2rfc some-draft.xml --pdf`