test+docs: live mainnet burn e2e verified; treasury rent-exempt requirement

End-to-end burn proven on mainnet (test wallet): build → sign → broadcast →
confirm → receipt → Essence. tx 5ddbmLRz… burned a dust token, closed the
account, returned 0.00197 SOL to the user, sent the 5% (103704 lamports) to the
treasury, recorded as Essence (Round #1 = 103704). Re-scan confirms the account
is gone; treasury credited; DB row written.

Discovered + documented: the treasury must be funded to rent-exemption before
collecting fees (a fee transfer into a 0-balance account fails "insufficient
funds for rent"). Noted in .env.example + design §3.1. Tracker: Phase 3 done.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/PYRE_MVP_DESIGN.md

@@ -120,6 +120,10 @@ fee is deliberately in the fair band:
   Spawn+claim+rounds = the differentiation.
 - Trust is the moat: always display net SOL + the exact fee before signing; never
   inject undisclosed instructions; never keep swap proceeds.
+- **Ops:** the treasury must be funded to rent-exemption (~0.0009 SOL) before it
+  collects fees, or the first fee transfer into a 0-balance account fails the tx
+  ("insufficient funds for rent"). Verified end-to-end on mainnet 2026-05-31
+  (burn→close→5% fee→Essence; tx 5ddbmLRz…).
 
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