Add todo.md with outstanding work list

Captures the four next-task buckets:
- Outreach (file issue on markqvist/Reticulum)
- Test infrastructure (bootstrap test-vectors/, write priority verifier scripts)
- Open UNVERIFIED items in SPEC.md to resolve
- Spec polishing (split SPEC.md, document Resource and Propagation /get)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

todo.md

@@ -0,0 +1,76 @@
+# TODO
+
+Outstanding work for the spec repo.
+
+## Outreach
+
+- [ ] **File a community-documentation issue on `markqvist/Reticulum`.**
+      Link this repo as a community-maintained byte-level spec. Ask
+      whether the maintainer would like to bless / link from the
+      official Reticulum manual. Frame it as a complement to (not a
+      replacement for) the existing operator-focused docs.
+
+## Test infrastructure
+
+- [ ] **Bootstrap `test-vectors/`** with the existing vectors from
+      `reticulum-mobile-app/reference/test-vectors.json`. Convert to
+      the proposed JSON format documented in `test-vectors/README.md`,
+      adding the regenerator scripts so future contributors can
+      verify vectors against newer upstream RNS releases.
+
+- [ ] **Write the priority verifier scripts** listed in
+      `tools/README.md`, in this order (highest interop value first):
+      1. `verify_destination_hash.py` — pure-function check, no RNS state needed
+      2. `verify_packet_header.py` — bit layout + HEADER_1/HEADER_2 round-trip
+      3. `verify_announce_roundtrip.py` — closes the SPEC.md §4 gap
+      4. `verify_token_crypto.py` — closes SPEC.md §3 gap
+      5. `verify_lxmf_opportunistic.py` — closes SPEC.md §5 gap
+      6. `verify_link_handshake.py` — closes SPEC.md §6 gap
+      7. `verify_path_request.py` — closes SPEC.md §7.1, §7.2 gaps
+      8. `verify_msgpack_quirk.py` — closes SPEC.md §9.3 gap
+
+      Each verifier should remove its corresponding `⚠️ UNVERIFIED` /
+      `🔮 SPECULATION` callout in `SPEC.md` (per `agent.md` §1).
+
+## Open `⚠️ UNVERIFIED` items in SPEC.md
+
+These need either a runtime test or a stronger upstream source citation
+to remove their markers:
+
+- [ ] **§2.3 Originator HEADER_1 → HEADER_2 conversion.** Need a
+      verifier that exercises `RNS.Transport.outbound` with a known
+      multi-hop path table and shows the wire bytes change.
+
+- [ ] **§4.3 The 3-element `[name, stamp_cost, [capabilities]]`
+      app_data variant.** Need a captured upstream emission with the
+      capabilities field present, ideally with `SF_COMPRESSION` set.
+
+- [ ] **§7.1 path? always precedes LXMF DATA.** Verify whether peers
+      ALWAYS issue path? before sending LXMF, or only when the path
+      table entry is stale. Run a controlled test with a fresh path
+      and a known-stale path.
+
+- [ ] **§7.4 Ratchet ring count default = 8.** Find the upstream
+      source citation (`RNS/Identity.py`, search for `RATCHET_COUNT`
+      or similar). Update SPEC.md with the file + line, OR replace
+      with the actual measured value if different.
+
+## Spec polishing (lower priority)
+
+- [ ] **Split `SPEC.md` into per-layer files** as the document grows
+      past ~1500 lines. Suggested layout per `README.md`:
+      `00-overview.md`, `01-packet-header.md`, `02-identity.md`,
+      `03-announce.md`, `04-token-crypto.md`, `05-lxmf.md`,
+      `06-link.md`, `07-resource.md`, `08-transport.md`,
+      `09-paths-and-discovery.md`, `10-implementation-gotchas.md`.
+
+- [ ] **Add a "last-verified-against-rns" line** to SPEC.md
+      frontmatter (per `agent.md` §7) so readers know which RNS
+      version the spec was tested against.
+
+- [ ] **Document the Reticulum Resource fragmentation protocol** —
+      currently absent from SPEC.md but needed for multi-packet LXMF
+      over Link (NomadNet pages > 1 MTU, large file transfers).
+
+- [ ] **Document the Propagation `/get` pull protocol** for offline
+      message retrieval. Used by Sideband when peers are out of range.