Lands the high-priority fixes from the 2026-05-06 audit before any
mainnet submit of the new vote/cosign/advance/destroy txs.
## H-1: Locked→Finished gate (MCP tool)
`dao_proposal_advance_unsigned` now refuses LockedToFinished unless
`tx_lower_ms > executing_end`. During the executing period the
validator demands gstMoved=true (governor input present); builder
doesn't include the governor input, so a tx in that window would
fee-burn. The proper Locked→Finished + GAT-mint flow is Phase 4c-bis;
this gate keeps us out of the broken middle.
## H-2 + H-4: strict-boundary + tx-upper-inside-period (MCP tool)
Validator's pgetRelation is strict on PAfter (`period_end < lb`)
and demands `ub <= period_end` on PWithin. Tool now picks PWithin
only when `tx_lower_ms >= period_start && tx_upper_ms <= period_end`,
PAfter only when `tx_lower_ms > period_end` strictly, and explicit-
errors on the boundary-straddling case (when tx validity range
crosses out of the target period). Same logic mirrored for the
VotingReady→Locked + VotingReady→Finished branches.
## H-3: vote builder lower-bound preflight (MCP tool)
`dao_proposal_vote_unsigned` previously checked only validity_upper
vs voting_end_ms. Validator demands BOTH `voting_start <= lb` AND
`ub <= voting_end`. Vote-too-early would hit "too early or invalid"
script error. New preflight on tx_lower_ms vs voting_start.
## M-2: DRep deposit pulled from ProtocolParams
Hardcoded constant (500 ADA) was wrong if the protocol changes
drep_deposit OR if the DRep was originally registered at a different
deposit amount (deregistration must match registration). Added
`drep_deposit_lovelace: u64` to ProtocolParams (default 500 ADA),
governance.rs build_signed_drep_registration / deregistration now
read from params instead of the constant. Constant kept for
backward compat with a doc note pointing at the params field.
## Pallas fork bump 507fd9da → 8091abd1
M-4 from the audit landed on the fork: voting_procedures builder
debug_assert_ne!s against empty CBOR map (0xa0) and docs the
upstream NonEmptyKeyValuePairs::decode footgun.
L-1 from the audit was a false finding — the audit subagent
misread the constants. PROPOSAL_CREATE_*_EX_UNITS are already at
the post-2026-05-05-H-2 values (5M mem / 2G steps per spend, 2M / 1G
per mint). The new builders alias these correctly. No change needed.