feat: persist and dispatch client command input

internal/client/spool/migrations.go

@@ -13,7 +13,10 @@ type migration struct {
 	sql     string
 }
 
-var migrations = []migration{{version: 1, sql: schemaV1}}
+var migrations = []migration{
+	{version: 1, sql: schemaV1},
+	{version: 2, sql: schemaV2},
+}
 
 func applyMigrations(ctx context.Context, db *sql.DB) error {
 	if _, err := db.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
@@ -113,3 +116,19 @@ CREATE TABLE command_tombstones (
 ) STRICT;
 CREATE INDEX tombstones_fifo ON command_tombstones(acknowledged_at, issue_uuid);
 `
+
+// schemaV2 adds the immutable execution specification retained with every
+// accepted dispatch. Keeping it in its own table lets old commands created by
+// early development builds (which have no specification) remain readable and
+// makes the payload's quota charge independently auditable.
+const schemaV2 = `
+CREATE TABLE command_specs (
+  issue_uuid BLOB PRIMARY KEY REFERENCES commands(issue_uuid) ON DELETE CASCADE CHECK(length(issue_uuid) = 16),
+  raw_bytes INTEGER NOT NULL CHECK(raw_bytes > 0),
+  stored_bytes INTEGER NOT NULL CHECK(stored_bytes > 0),
+  compression INTEGER NOT NULL CHECK(compression = 2),
+  payload BLOB NOT NULL,
+  payload_sha256 BLOB NOT NULL CHECK(length(payload_sha256) = 32),
+  charged_bytes INTEGER NOT NULL CHECK(charged_bytes > 0)
+) STRICT, WITHOUT ROWID;
+`