Cardano Updates

Move six closed-form cert-deposit helpers from
src/Ledger/Dijkstra/Specification/Utxo.lagda.md to
src/Ledger/Dijkstra/Specification/Certs.lagda.md:

  + updateCertDeposit
  + updateCertDepositsStep  (new named extraction of the fold body)
  + updateCertDeposits
  + coinFromDeposits
  + depositsChange
  + newCertDeposits
  + refundCertDeposits

These helpers depend only on Certs-level definitions, so their natural
home is Certs.lagda.md.  Their placement in Utxo.lagda.md forced any
proof referencing them to take the larger TransactionStructure /
AbstractFunctions parameter set, blocking proofs in
Certs.Properties.PoV(Lemmas) (parameterised only by GovStructure) from
referring to them.

govProposalsDeposits stays in Utxo.lagda.md — it depends on GovProposal
from Gov.Actions, not on a Certs-level type.

Bundled bug fixes to updateCertDeposits:

  + Typo: DState.deposits was being set from the GState delta instead
    of the DState delta.

  + Fold direction: was foldr (right-to-left).  CERTS processes certs
    left-to-right via BS-ind's head-first decomposition.  Changed to
    foldl, matching Conway's left-to-right recursion and Dijkstra's
    own applyToRewards.  Counterexample under foldr:
    [delegate c d, dereg c (just d)] on a fresh credential should
    leave c ∉ deposits per CERTS, but foldr processes dereg first
    (a no-op) then delegate, ending with c ∈ deposits.

updateCertDepositsStep is the inner fold body extracted as a named
function so downstream proofs in Certs.Properties.PoV can state and
use a per-step pots equation about it.

Also: add HasCoin-UTxOState (Utxo.lagda.md) and HasCoin-LedgerState
(Ledger.lagda.md).  HasCoin-LedgerState sums UTxO state total, DState
rewards balance, and the three deposit pots via the hoisted
coinFromDeposits — the form needed to balance against the UTXO
batch-balance equation.

Closes #1208.

Adds the per-step and RTC-induction bridging lemmas that prove the actual `CertState` produced by a `CERTS` chain has the same three deposit pots (and hence the same `coinFromDeposits`) as the closed-form `updateCertDeposits` applied to the initial state and the cert list.  This is the cert-deposit half of the `LEDGER-pov` chain; combined with the `posNeg-deposits` cancellation identity, it closes the deposit-accounting equation against the UTXO batch-balance equation.

New proofs (PR branch):

+  `CERT-deposits-updateCertDeposit` in `Certs.Properties.PoVLemmas`.  Per-step, case-split on the `CERT` rule's eight `DCert` constructors; `refl` in seven cases, `POOL-rereg` discharged via the pool-deposit alignment invariant.

+  `CERTS-deposits-updateCertDeposits` in `Certs.Properties.PoV`.  RTC induction mirroring `CERTS-pov`.  Factored through `updateCertDeposit-list`, a pure pot-only `foldl` that is the rule-intrinsic counterpart of `updateCertDeposits`; the bridge `pots-updateCertDeposits` handles the inheritance of non-deposit `CertState` fields.

+  `CERTS-coinFromDeposits-updateCertDeposits`.  Coin projection of the main lemma, immediately usable by `LEDGER-pov`.

Both bridging lemmas are parameterised over (a) two deferred set/map facts (`∪ˡ-singleton-mem-≡`, `Is-just-isPoolRegistered⇒∈-dom`) to be discharged from the standard library; and (b) the pool-deposit alignment invariant `PoolDepositsAligned` plus, for the RTC sibling, its `CERT`-step preservation lemma — both follow by inspection of the `POOL` sub-rules.

Master-touching changes

+  **Bug fix in `updateCertDeposits`**.  Was setting `DState.deposits` to `depositsᵍ` (the `GState` delta) instead of `depositsᵈ`.  The `depositsᵈ` name was bound by destructuring but otherwise unused — almost certainly an unintended typo.

+  **Bug fix in `updateCertDeposits`**.  Was using `foldr`, processing certs right-to-left.  The `CERTS` rule processes certs left-to-right (via `BS-ind`'s head-first decomposition).  For non-commutative cert sequences this is unsound: e.g. `[delegate c keyDeposit, dereg c (just keyDeposit)]` for a fresh credential should end with `c ∉ deposits` per `CERTS`, but `foldr` (which processes the `dereg` on the fresh state first as a no-op, then the `delegate`) ends with `c ∈ deposits`.  Switched to `foldl`.  Conway's `updateCertDeposits` is recursive left-to-right (equivalent to `foldl`); Dijkstra's own `applyToRewards` uses `foldl`.

+  **Refactor**.  Extracted `updateCertDepositsStep` as a named function from `updateCertDeposits`' inner lambda, so that downstream proofs can state and use its per-step pots equation.

+  **Hoist**.  Moved `updateCertDeposit`, `updateCertDeposits`, `coinFromDeposits`, `depositsChange`, `newCertDeposits`, `refundCertDeposits` from `Utxo.lagda.md` to `Certs.lagda.md`.  These depend only on `Certs`-level definitions (`PParams`, `DCert`, `CertState`); the previous location forced any proof referencing them to take the larger `TransactionStructure` / `AbstractFunctions` parameter set, blocking placement of the bridging lemmas in `Certs.Properties.PoV{,Lemmas}`.  `govProposalsDeposits` remains in `Utxo.lagda.md` (depends on `GovProposal`).

PR-branch-only changes:

+  `Ledger.lagda.md`. Replaced the local `coinFromDeposit` (singular) with the hoisted `coinFromDeposits` (plural).  `HasCoin-LedgerState` has three summands: `getCoin(UTxOState) + rewardsBalance(DState) + coinFromDeposits(CertState)`.  Gov-action deposits are stored in `GState.deposits` (keyed by `returnAddr`'s stake credential) and are therefore already counted by the third summand.

mkdocs .md files weren't being generated even when .lagda.md files changed.

* Add utxo0 binding in UTXOW

For consistency with SUBUTXOW

* Add missing premises

* Improve tc time of Utxo.Computational

mkdocs .md files weren't being generated even when .lagda.md files changed.

For consistency with SUBUTXOW

* Remove DepositsChange

Calculate deposit changes from CertState and certificates in the tx

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Co-authored-by: William DeMeo <[email protected]>