G C-4: mesh/ledger.remove with its request and answer, and the capability words of the bus-state families

Builds: design 47 G §587, §462, §622

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

go/buscalls/buscalls.go

@@ -44,8 +44,11 @@ const (
 	LedgerHistory = "mesh/ledger.history"
 	LedgerWatch   = "mesh/ledger.watch"
 	LedgerQuery   = "mesh/ledger.query"
-	// LedgerFill is one ledger's fill against its cap, answered as a Fill (design 47 G §462).
-	LedgerFill = "mesh/ledger.fill"
+	// LedgerFill is one ledger's history's fill against its cap, asked with a LedgerRequest and answered as a Fill
+	// (design 47 G §462, §587); LedgerRemove removes one instance, asked with a LedgerRemoveRequest and answered as
+	// LedgerRemoved. Both are under the capability word LedgerUpkeepCalls.
+	LedgerFill   = "mesh/ledger.fill"
+	LedgerRemove = "mesh/ledger.remove"
 	// The ledger's repairs, which the tool runner also serves as tools of every module owning a ledger, its own
 	// ledgers only (design 25 § 12.5).
 	LedgerRebuild  = "mesh/ledger.rebuild"
@@ -54,6 +57,16 @@ const (
 	LedgerLag      = "mesh/ledger.lag"
 )
 
+// The capability words of the families this package's calls belong to (design 47 G §488, §622): a tool runner states a
+// word once it answers the family, and a bundle fails at once, naming the word and its node, on a call whose word is not
+// stated. Which calls each word covers is the tool runner's (§462).
+const (
+	BusStateCalls     = "bus-state-calls"
+	LedgerCalls       = "ledger-calls"
+	LedgerUpkeepCalls = "ledger-upkeep-calls"
+	SentObjectsCalls  = "sent-objects-calls"
+)
+
 // The methods the tool runner sends the bundle for a watch it asked, each naming the watch by its id, as `mesh/log`
 // does for a log.
 const (
@@ -371,6 +384,21 @@ type LedgerRequest struct {
 	Ledger string `json:"ledger"`
 }
 
+// LedgerRemoveRequest names one instance of a ledger to remove from its history, its state and its indexes (design 47 G
+// §587).
+type LedgerRemoveRequest struct {
+	Ledger   string `json:"ledger"`
+	Instance string `json:"instance"`
+}
+
+// LedgerRemoved is remove's answer: the instance, the operations removed and the bytes the history held less after it;
+// an instance the ledger does not hold answers 0 and 0, so a removal said twice changes nothing.
+type LedgerRemoved struct {
+	Instance   string `json:"instance"`
+	Operations uint64 `json:"operations"`
+	Bytes      uint64 `json:"bytes"`
+}
+
 // Repaired is the answer of rebuild, reindex and snapshot: how many instances (or index entries) it wrote.
 type Repaired struct {
 	Written int `json:"written"`