docs: record external design-review items (positioning, claim precision, anti-over-expansion)

From an outside critique of the stack. The high-priority items are claim
precision (a hosted-DB service is not 'no server of record') and the
positioning reframe (four primitives + Tessera as the proof they compose),
plus the discipline to resist adding a fifth infrastructure layer.

Co-Authored-By: Claude Opus 4.8 <[email protected]>
Claude-Session: https://claude.ai/code/session_01BXQCvJPA6sVSQ5j8uBd9bB

docs/TODO.md

@@ -0,0 +1,42 @@
+# BitBlocks — TODO
+
+The umbrella site + narrative for the stack (BitLogin · BitGate · BitFeed ·
+BitUnlock, and Tessera as the worked example).
+
+## Design review — external critique (2026-08-11)
+
+An outside review of the whole stack (concept rated ~9/10). The concept is
+strong; the actionable notes are precision and positioning, which matter a lot
+for security infrastructure. Distilled, with our take:
+
+### Positioning
+- **[agree] Stop calling all five things "primitives."** Tessera is an
+  application built WITH the stack, not a fifth primitive. Reframe as
+  **"Four primitives. One proof they compose."** — a PRIMITIVES tier
+  (BitLogin · BitGate · BitFeed · BitUnlock) and a BUILT-WITH tier (Tessera,
+  then future apps). A stronger story than forced five-way symmetry.
+- **[agree] Add one architecture diagram:** Nostr / Lightning → the four blocks
+  → Tessera / future apps. Communicates the whole project in ~ten seconds.
+- **[agree] Sharpen the thesis:** "BitBlocks is an application architecture in
+  which identity, policy, discovery, payments, and capabilities are portable
+  objects rather than proprietary backend services — the client becomes the
+  disposable part." Keep the hero line ("The web made you a tenant. Own the
+  stack.").
+
+### Claim precision (highest priority — this is security infra)
+- **[strongly agree] "No server of record" overclaims.** BitUnlock is a hosted
+  service with a D1 database. Reframe the principle to **"No platform-owned
+  source of truth"** / "Portable state first, replaceable services where
+  services are necessary." Servers are allowed; a server OWNING the user is not.
+- **[strongly agree] Drop impossibility claims** like "no one can delete your
+  history." Relay retention is best-effort (BitLogin's own docs say so). Use
+  "no single operator controls…", "portable across…", "doesn't depend on one
+  host…". Audit every absolute claim on the umbrella page AND each block site.
+
+### Strategy
+- **[agree] Resist over-expansion.** We have enough primitives. The validation
+  goal is NOT a fifth infrastructure layer — it's a SECOND, radically different
+  application on the same four blocks with no special-casing. Two unlike apps
+  composing cleanly from the four primitives proves an *architecture*, not a
+  product family. That's the north star; let real application pressure decide
+  what the stack is missing.