Fuzz: tip → withdraw → unregister roundtrip

[nanaf6203-bit]

Problem Statement
Existing fuzz tests stop at "balance goes back to zero". The actual
final unregister step is not covered by fuzz.

Why it matters
unregister walks CreatorTokens and counts balances — a corner-case
harness closure.

Acceptance Criteria

• A test_full_lifecycle property test: random tip amounts and
  patterns, full withdraw, then unregister and asserts cleanup.

Files/Modules Likely Affected

• src/fuzz.rs

Difficulty Easy. Estimated Effort S.

Labels
area:testing, area:fuzzing, priority:medium

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Imported from docs/open-issues-draft.md as draft issue #31 (commit 7becd4b). Original draft-order cross-references in this body have been remapped to current GitHub issue numbers at import time.

[GBOYEE]

Hi team — I'd like to take this on as part of the GrantFox campaign. I'll implement this and open a PR shortly.