test: assert storage creation-fee burn through the e2e path

[adamkrellenstein]

Stacked on #441 (feat/storage-economics). Closes part of the economic-e2e gap surfaced by the test-strategy audit: no test asserted an economic state transition through block processing.

What

filestorage_create_and_get previously asserted the storage creation fee υ_f was charged (fee > 0) but not that it was actually burned from total supply. This adds a supply-conservation assertion around create_agreement:

• total supply strictly decreases across the call (the fee is burned), and
• the drop is at least the returned created.fee (the remainder is gas, also burned).

filestorage_create_and_get is part of the dual-mode test_file_storage_regtest body, so the assertion runs:

• in-process via the _local variant (verified locally), and
• end-to-end via the regtest variant in CI — a mined Bitcoin block → indexer → contract → asserted supply change.

That's the missing leg: an economic state transition asserted through real block processing, not just an in-process property loop.

Design decisions

• >= fee, not == fee. The supply drop is fee + gas (gas is also burned), so an exact-equality assertion is wrong; the robust invariant is strict decrease plus drop ≥ fee. Confirmed empirically (the exact form failed by exactly the gas amount).
• Reused an existing dual-mode test rather than adding a new one — filestorage_create_and_get already uses a real PoR descriptor that passes in both lite and regtest modes, avoiding the trivial-root rejection that a fresh make_descriptor would hit under regtest.
• Added a token import! to the module to read total_supply (mirrors staking_contract.rs).

Scope note

The deeper economic-e2e paths — ordering-reward accrual and challenge-failure → slash through block processing — remain blocked on the reactor↔economics wiring (#442) and are out of scope here. This PR covers the user-driven path (creation-fee burn) that is drivable end-to-end today.

Merge order

Touches native_filestorage_contract.rs, which #456 and #452 also modify. Merge after #441; coordinate with #452 (impl) / #456 (property tests) — additive changes, rebase whichever merges last.

🤖 Generated with Claude Code

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Note

Low Risk
Test-only changes to contract integration tests; no production logic or auth paths modified.

Overview
Extends filestorage_create_and_get so storage agreement creation is checked against token total supply, not only that created.fee > 0. The test now snapshots supply before/after create_agreement, asserts supply strictly decreases, and that the drop is at least the creation fee υ_f (allowing additional burn from gas).

A token WIT import! is added so the test can call token::total_supply. Because this helper runs under run_regtest / test_file_storage_regtest, the same assertions apply in-process and on the regtest path (mined block → indexer → contract).

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