rename project to MultiforaDB

Prose and benchmark tables use MultiforaDB; the binary, the CLI usage
line, the log-message prefix and the default database file use
multiforadb.

Two consequences worth noting:

- build.zig.zon's fingerprint is derived from the package name, so it
  had to change with it (Zig refuses to build otherwise). A consumer
  pinning this package by fingerprint needs updating.
- the default --db path is now multiforadb.log, and getCmdLineOpts
  reports it as dbpath. An existing mongo-lite.log has to be passed
  explicitly with --db.

The e2e harness abbreviated the old name as ML_; that is now MFDB_,
including the documented ML_BIN override (MFDB_BIN) and the scratch
file names. MD_ (mongod) is untouched.

compare-run.sh spawned the server by absolute path under a
sandbox/mongo-lite directory that no longer exists; that block already
runs from tests/e2e, so it uses a relative path now.

The archived reports under tests/e2e/results/ keep the old name: they
record what the old binary measured.

src/db.zig

@@ -986,7 +986,7 @@ pub const Engine = struct {
         // epilogue called us.
         self.request_compact();
         std.debug.print(
-            "mongo-lite: compaction gave up after {d} attempts (concurrent writes); will retry\n",
+            "multiforadb: compaction gave up after {d} attempts (concurrent writes); will retry\n",
             .{attempt_max},
         );
     }
@@ -1045,7 +1045,7 @@ pub const Engine = struct {
         while (doc_it.next()) |doc_entry| {
             ix.append_doc_entries(self.gpa, coll.doc_bytes(doc_entry.value_ptr.*), doc_entry.key_ptr.*) catch |err| switch (err) {
                 error.ParallelArrays => {
-                    std.debug.print("mongo-lite: WARNING: index '{s}' cannot index an existing document; entry skipped\n", .{ix.name});
+                    std.debug.print("multiforadb: WARNING: index '{s}' cannot index an existing document; entry skipped\n", .{ix.name});
                     continue;
                 },
                 else => return err,
@@ -1053,7 +1053,7 @@ pub const Engine = struct {
         }
         // Tolerated, not enforced: the database must always open.
         if (try ix.finish_bulk(self.gpa, false)) {
-            std.debug.print("mongo-lite: WARNING: unique index '{s}' has duplicate keys in existing data; duplicates not enforced for existing documents\n", .{ix.name});
+            std.debug.print("multiforadb: WARNING: unique index '{s}' has duplicate keys in existing data; duplicates not enforced for existing documents\n", .{ix.name});
         }
     }
 
@@ -1103,7 +1103,7 @@ fn apply_record(ctx: *anyopaque, record: storage.Record, doc: *bson.Document) an
     switch (record.type) {
         storage.record_type_index_create => {
             self.register_index_from_spec(coll, doc) catch |err| {
-                std.debug.print("mongo-lite: index create record failed to apply: {s}\n", .{@errorName(err)});
+                std.debug.print("multiforadb: index create record failed to apply: {s}\n", .{@errorName(err)});
                 return;
             };
             return;
@@ -1121,7 +1121,7 @@ fn apply_record(ctx: *anyopaque, record: storage.Record, doc: *bson.Document) an
     }
 
     const id_value = doc.get("_id") orelse {
-        std.debug.print("mongo-lite: log record without _id, skipping\n", .{});
+        std.debug.print("multiforadb: log record without _id, skipping\n", .{});
         return;
     };
     const id_key = try bson.serialize_value(self.gpa, id_value);