fix(economic): decode the 0x0032 bundle-acceptance leaf — a trader who settled could admit nothing again

[cryptskii]

A live defect on main since #852, found while implementing the C2 cutover. Landed separately and first: it is its own topic, and C2's walk depends on it.

What broke

#852 made the bundle-acceptance leaf (0x0032) mandatory in every market settle's write set, and added the fifth EconomicLeafState arm's encoder, key, value — and even its arm in the pre-state match — but not its decoder arm. read_leaf_state fell through to WrongClass for 0x0032.

path	consequence since #852
producer_tree_and_pre_state	every admission rebuilds its pre-state from the leaf cache, which after a settle holds the acceptance leaf — a trader who settled once could admit nothing again: no send, no second trade
resume_pending_admission	a crash-resumed settle could not decode its own frozen witness
peer lineage walk	a peer walking a trader through a settle read the witness as INVALID
economic proof artifacts	a settle's inclusion proof did not decode

The first row is established by execution. With the arm removed, the new end-to-end test fails on a genuine settle with:

decode cached leaf state: unexpected object class 0x0032

The fix

The missing arm, mirroring the encoder exactly — envelope and two digest32, no rejection. The encoder refuses nothing; a decoder stricter than its encoder makes valid leaves unreadable.

The guard

every_leaf_class_round_trips_through_the_decoder matches every EconomicLeafState arm with no wildcard. A sixth arm fails to compile there until a sample is added, and the sample fails at runtime until the decoder handles it. #852 slipped because no test ever decoded the leaf it added.

Controls — each executed red with the arm removed, green with it

test	what it decodes
every_leaf_class_round_trips_through_the_decoder	one sample of every leaf class
a_settle_witness_carrying_the_acceptance_leaf_decodes_to_itself	a real settle witness from build_write_set
an_artifact_proving_a_bundle_acceptance_leaf_decodes_and_verifies	a settle's inclusion proof
a_trader_that_settled_can_still_build_its_next_pre_state	live route, end to end

Dependent sweep: nothing asserted the old failure.

Verification

economic_provenance_wire              18/18
trader_acceptance_producer             9/9
economic::proof_artifact               7/7
dlv_routes new end-to-end control      1/1
make lint                             exit 0
ci/production_safety_checks.sh        exit 0