docs: update status with mesh infrastructure progress

Completed in this session:
- KeyPackage distribution over mesh (announce-based)
- Transport capability negotiation
- MLS-Lite to full MLS upgrade path

Updated mesh-protocol-gaps.md to reflect completed items.

docs/status.md

@@ -47,9 +47,23 @@ New `fapp_router.rs` module:
 
 ---
 
-## 2026-03-30 — Implementation Sprint (S4-S5 + MLS-Lite)
+## 2026-03-30 — Mesh Protocol Infrastructure Sprint
 
-### Completed
+### Completed (Latest)
+- **KeyPackage distribution** — `keypackage_cache.rs` + `mesh_protocol.rs`
+  - MeshAnnounce extended with `keypackage_hash` field
+  - KeyPackageRequest/Response/Unavailable messages
+  - KeyPackageCache with TTL, per-address limits, LRU eviction
+- **Transport capability negotiation** — `transport.rs` TransportCapability
+  - Auto-classification: Unconstrained/Medium/Constrained/SeverelyConstrained
+  - CryptoMode recommendation per capability level
+  - TransportManager.recommended_crypto(), select_for_size()
+- **MLS-Lite upgrade path** — `crypto_negotiation.rs`
+  - GroupCryptoState tracks current mode
+  - MlsLiteBootstrap derives MLS-Lite keys from MLS epoch secret
+  - Enables same group to use full MLS on WiFi, MLS-Lite on LoRa
+
+### Previously Completed
 - **S4: Multi-hop routing** — `MeshRouter` with `send()`, `handle_incoming()`, `forward()`, `drain_store_for()`
 - **S4: REPL commands** — `/mesh trace <address>` and `/mesh stats`
 - **S5: Truncated addresses** — `MeshEnvelopeV2` with 16-byte addresses (~18% smaller)