feat(update): add OverwriteFiles for overwrite snapshot commits

Summary:
Add a production OverwriteFiles builder that brings iceberg-cpp to semantic
parity with Java's BaseOverwriteFiles. It supports explicit file replacement
(DeleteFile + AddFile) and range-based replacement (OverwriteByRowFilter +
AddFile) with the same family of pre-commit concurrency validations. The
builder is a thin subclass of MergingSnapshotUpdate and reuses the existing
commit kernel (Apply/summary/retry/cleanup) unchanged.

Changes:
- New OverwriteFiles class (src/iceberg/update/overwrite_files.{h,cc}) and
  Table::NewOverwrite() / Transaction::NewOverwrite() entry points.
- Builder surface: AddFile, DeleteFile, bulk DeleteFiles, OverwriteByRowFilter,
  ValidateFromSnapshot, ConflictDetectionFilter, ValidateNoConflictingData,
  ValidateNoConflictingDeletes, ValidateAddedFilesMatchOverwriteFilter,
  WithCaseSensitivity.
- Validate(): conflict-filter resolution, concurrent add/delete conflict checks,
  and strict added-file range validation (projection + StrictMetricsEvaluator).
- Tests (overwrite_files_test.cc, 45 cases) and CMake/meson wiring.

Behavior alignment with Java:
- operation() returns append/delete/overwrite from builder content.
- Conflict-filter resolution mirrors BaseOverwriteFiles (explicit -> row filter
  -> AlwaysTrue); replaced-file delete checks honor ConflictDetectionFilter.
- Strict added-file validation uses a single DataSpec(), rejecting multi-spec
  and empty added-file sets.
- Deviations: public WithCaseSensitivity (vs caseSensitive) to avoid a
  protected-name clash; ValidateFromSnapshot rejects negative ids early.

Author: shuxu.li

src/iceberg/CMakeLists.txt

@@ -97,6 +97,7 @@ set(ICEBERG_SOURCES
     update/expire_snapshots.cc
     update/fast_append.cc
     update/merging_snapshot_update.cc
+    update/overwrite_files.cc
     update/pending_update.cc
     update/set_snapshot.cc
     update/snapshot_manager.cc

src/iceberg/meson.build

@@ -119,6 +119,7 @@ iceberg_sources = files(
     'update/expire_snapshots.cc',
     'update/fast_append.cc',
     'update/merging_snapshot_update.cc',
+    'update/overwrite_files.cc',
     'update/pending_update.cc',
     'update/set_snapshot.cc',
     'update/snapshot_manager.cc',

src/iceberg/table.cc

@@ -33,6 +33,7 @@
 #include "iceberg/transaction.h"
 #include "iceberg/update/expire_snapshots.h"
 #include "iceberg/update/fast_append.h"
+#include "iceberg/update/overwrite_files.h"
 #include "iceberg/update/set_snapshot.h"
 #include "iceberg/update/snapshot_manager.h"
 #include "iceberg/update/update_location.h"
@@ -217,6 +218,12 @@ Result<std::shared_ptr<FastAppend>> Table::NewFastAppend() {
   return FastAppend::Make(name().name, std::move(ctx));
 }
 
+Result<std::shared_ptr<OverwriteFiles>> Table::NewOverwrite() {
+  ICEBERG_ASSIGN_OR_RAISE(
+      auto ctx, TransactionContext::Make(shared_from_this(), TransactionKind::kUpdate));
+  return OverwriteFiles::Make(name().name, std::move(ctx));
+}
+
 Result<std::shared_ptr<UpdateStatistics>> Table::NewUpdateStatistics() {
   ICEBERG_ASSIGN_OR_RAISE(
       auto ctx, TransactionContext::Make(shared_from_this(), TransactionKind::kUpdate));

src/iceberg/table.h

@@ -176,6 +176,9 @@ class ICEBERG_EXPORT Table : public std::enable_shared_from_this<Table> {
   /// \brief Create a new FastAppend to append data files and commit the changes.
   virtual Result<std::shared_ptr<FastAppend>> NewFastAppend();
 
+  /// \brief Create a new OverwriteFiles to overwrite data files and commit the changes.
+  virtual Result<std::shared_ptr<OverwriteFiles>> NewOverwrite();
+
   /// \brief Create a new SnapshotManager to manage snapshots and snapshot references.
   virtual Result<std::shared_ptr<SnapshotManager>> NewSnapshotManager();
 

src/iceberg/test/CMakeLists.txt

@@ -232,7 +232,8 @@ if(ICEBERG_BUILD_BUNDLE)
                    update_properties_test.cc
                    update_schema_test.cc
                    update_sort_order_test.cc
-                   update_statistics_test.cc)
+                   update_statistics_test.cc
+                   overwrite_files_test.cc)
 
   add_iceberg_test(data_test
                    USE_BUNDLE

src/iceberg/test/meson.build

@@ -120,6 +120,10 @@ iceberg_tests = {
         ),
         'use_data': true,
     },
+    'overwrite_files_test': {
+        'sources': files('overwrite_files_test.cc'),
+        'use_data': true,
+    },
 }
 
 if get_option('rest').enabled()