fix: use existing page size when opening pre-built database snapshots

The database fixtures are generated on macOS (Apple Silicon, 16KB pages)
but CI runs on Linux (x86_64, 4KB pages). DbEnvBuilder was always
forcing the OS default page size via set_geometry, causing MDBX to
report MDBX_CORRUPTED when the forced page size didn't match the
existing database's page size.

Add `existing_page_size()` to DbEnvBuilder that sets page_size to None,
letting MDBX read the page size from the existing data file. Use it in
Db::open_no_sync which is specifically for opening pre-built snapshots.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kariy

crates/storage/db/src/lib.rs

@@ -165,6 +165,7 @@ impl Db {
             .max_size(GIGABYTE * 10)
             .growth_step((GIGABYTE / 2) as isize)
             .sync(SyncMode::UtterlyNoSync)
+            .existing_page_size()
             .build(path)?;
 
         env.create_default_tables()?;

crates/storage/db/src/mdbx/mod.rs

@@ -33,6 +33,7 @@ pub struct DbEnvBuilder {
     max_readers: u64,
     max_size: usize,
     growth_step: isize,
+    page_size: Option<PageSize>,
 }
 
 impl DbEnvBuilder {
@@ -43,6 +44,7 @@ impl DbEnvBuilder {
             max_readers: DEFAULT_MAX_READERS,
             max_size: DEFAULT_MAX_SIZE,
             growth_step: DEFAULT_GROWTH_STEP,
+            page_size: Some(PageSize::Set(utils::default_page_size())),
         }
     }
 
@@ -72,6 +74,15 @@ impl DbEnvBuilder {
         self
     }
 
+    /// Uses the page size from an existing database instead of forcing the OS default.
+    ///
+    /// This is required when opening databases created on a platform with a different
+    /// page size (e.g., macOS Apple Silicon uses 16KB pages vs Linux x86_64 4KB pages).
+    pub fn existing_page_size(mut self) -> Self {
+        self.page_size = None;
+        self
+    }
+
     /// Builds the database environment at the specified path.
     pub fn build(self, path: impl AsRef<Path>) -> Result<DbEnv, DatabaseError> {
         let mut builder = libmdbx::Environment::builder();
@@ -85,7 +96,7 @@ impl DbEnvBuilder {
                 growth_step: Some(self.growth_step),
                 // The database never shrinks
                 shrink_threshold: None,
-                page_size: Some(PageSize::Set(utils::default_page_size())),
+                page_size: self.page_size,
             })
             .set_flags(EnvironmentFlags {
                 mode: self.mode,