docs(backlog): pub/sub delivery leaks {:text,_} for CBOR text strings

Delivered fact payloads surface CBOR text strings (major 3) as {text, binary}
tuples instead of plain binaries, forcing every text-string consumer to unwrap
or crash on String.Chars. Two band-aids already in macula-realm. Proper fix:
delivery decode returns text as plain binary. See BACKLOG.md.

Author: rgfaber

BACKLOG.md

@@ -0,0 +1,39 @@
+# Macula SDK — Backlog
+
+Tracked work items not yet scheduled. Newest first.
+
+---
+
+## Pub/Sub delivery leaks `{:text, _}` for CBOR text strings
+
+**Filed:** 2026-06-01
+**Severity:** medium (correctness / consumer ergonomics; no data loss)
+
+Delivered pub/sub fact payloads surface CBOR **text strings (major 3)** as
+`{text, binary()}` tuples (Elixir `{:text, bin}`) — in map KEYS and VALUES, at
+any depth — instead of plain binaries. CBOR **byte strings (major 2)** correctly
+decode to plain binaries, so the leak only bites publishers that emit text
+strings (e.g. `hecate-parksim` → the `macula-realm` ClankerCab demo).
+
+**Impact:** every consumer of a text-string fact must defensively unwrap
+`{:text, _}` or it crashes the moment a key/value reaches `String.Chars`
+interpolation. This already forced two band-aids in `macula-realm`:
+- `clanker_cab_subscriber.ex` — recursive `{:text, bin}` → `bin` normalize at
+  the subscriber boundary (commit `52bc2d2`).
+- `topology/mesh_subscriber.ex` — the same `normalize/1` at `decode_record` +
+  `decode_app_payload`, a `{:text, _}` clause in `get_str/2`, and a hardcoded
+  `Map.get(payload, {:text, "superseded_key"})` tombstone lookup.
+
+**Proper fix:** pub/sub delivery decode should return CBOR text strings as plain
+`binary()` (matching byte-string behaviour), not `{text, _}` tuples. The
+`{text, binary()}` representation is `macula_record_cbor`'s internal canonical
+form (correct for deterministic sig encoding) — it should not surface in the
+app-facing decoded payload. Likely fix point: the SDK delivery/decode path that
+hands the fact term to subscribers (where it currently preserves the
+`macula_record_cbor` value rep instead of converting major-3 to binary).
+
+**When done:** drop the two normalize band-aids in `macula-realm` (search for
+`TODO(macula)` and the ClankerCab `normalize/1`).
+
+**Likely introduced:** a macula version between the realm's prior pinned build
+and 4.8.0 (the realm's ClankerCab worked with plain binaries before the bump).