feat(remote.mount): add -metadataStrategy flag to control metadata caching (#8568)

* feat(remote): add -noSync flag to skip upfront metadata pull on mount

Made-with: Cursor

* refactor(remote): split mount setup from metadata sync

Extract ensureMountDirectory for create/validate; call pullMetadata
directly when sync is needed. Caller controls sync step for -noSync.

Made-with: Cursor

* fix(remote): validate mount root when -noSync so bad bucket/creds fail fast

When -noSync is used, perform a cheap remote check (ListBuckets and
verify bucket exists) instead of skipping all remote I/O. Invalid
buckets or credentials now fail at mount time.

Made-with: Cursor

* test(remote): add TestRemoteMountNoSync for -noSync mount and persisted mapping

Made-with: Cursor

* test(remote): assert no upfront metadata after -noSync mount

After remote.mount -noSync, run fs.ls on the mount dir and assert empty
listing so the test fails if pullMetadata was invoked eagerly.

Made-with: Cursor

* fix(remote): propagate non-ErrNotFound lookup errors in ensureMountDirectory

Return lookupErr immediately for any LookupDirectoryEntry failure that
is not filer_pb.ErrNotFound, so only the not-found case creates the
entry and other lookup failures are reported to the caller.

Made-with: Cursor

* fix(remote): use errors.Is for ErrNotFound in ensureMountDirectory

Replace fragile strings.Contains(lookupErr.Error(), ...) with
errors.Is(lookupErr, filer_pb.ErrNotFound) before calling CreateEntry.

Made-with: Cursor

* fix(remote): use LookupEntry so ErrNotFound is recognised after gRPC

Raw gRPC LookupDirectoryEntry returns a status error, not the sentinel,
so errors.Is(lookupErr, filer_pb.ErrNotFound) was always false. Use
filer_pb.LookupEntry which normalises not-found to ErrNotFound so the
mount directory is created when missing.

Made-with: Cursor

* test(remote): ignore weed shell banner in TestRemoteMountNoSync fs.ls count

Exclude master/filer and prompt lines from entry count so the assertion
checks only actual fs.ls output for empty -noSync mount.

Made-with: Cursor

* fix(remote.mount): use 0755 for mount dir, document bucket-less early return

Made-with: Cursor

* feat(remote.mount): replace -noSync with -metadataStrategy=lazy|eager

- Add -metadataStrategy flag (eager default, lazy skips upfront metadata pull)
- Accept lazy/eager case-insensitively; reject invalid values with clear error
- Rename TestRemoteMountNoSync to TestRemoteMountMetadataStrategyLazy
- Add TestRemoteMountMetadataStrategyEager and TestRemoteMountMetadataStrategyInvalid

Made-with: Cursor

* fix(remote.mount): validate strategy and remote before creating mount directory

Move strategy validation and validateMountRoot (lazy path) before
ensureMountDirectory so that invalid strategies or bad bucket/credentials
fail without leaving orphaned directory entries in the filer.

* refactor(remote.mount): remove unused remote param from ensureMountDirectory

The remote *RemoteStorageLocation parameter was left over from the old
syncMetadata signature. Only remoteConf.Name is used inside the function.

* doc(remote.mount): add TODO for HeadBucket-style validation

validateMountRoot currently lists all buckets to verify one exists.
Note the need for a targeted BucketExists method in the interface.

* refactor(remote.mount): use MetadataStrategy type and constants

Replace raw string comparisons with a MetadataStrategy type and
MetadataStrategyEager/MetadataStrategyLazy constants for clarity
and compile-time safety.

* refactor(remote.mount): rename MetadataStrategy to MetadataCacheStrategy

More precisely describes the purpose: controlling how metadata is
cached from the remote, not metadata handling in general.

* fix(remote.mount): remove validateMountRoot from lazy path

Lazy mount's purpose is to skip remote I/O. Validating via ListBuckets
contradicts that, especially on accounts with many buckets. Invalid
buckets or credentials will surface on first lazy access instead.

* fix(test): handle shell exit 0 in TestRemoteMountMetadataStrategyInvalid

The weed shell process exits with code 0 even when individual commands
fail — errors appear in stdout. Check output instead of requiring a
non-nil error.

* test(remote.mount): remove metadataStrategy shell integration tests

These tests only verify string output from a shell process that always
exits 0 — they cannot meaningfully validate eager vs lazy behavior
without a real remote backend.

---------

Co-authored-by: Chris Lu <chris.lu@gmail.com>

weed/shell/command_remote_mount_buckets.go

@@ -109,9 +109,11 @@ func (c *commandRemoteMountBuckets) Do(args []string, commandEnv *CommandEnv, wr
 				Path:   "/",
 			}
 
-			// sync metadata from remote
-			if err = syncMetadata(commandEnv, writer, string(dir), true, remoteConf, remoteStorageLocation); err != nil {
-				return fmt.Errorf("pull metadata on %+v: %v", remoteStorageLocation, err)
+			if err = ensureMountDirectory(commandEnv, string(dir), true, remoteConf); err != nil {
+				return fmt.Errorf("mount setup on %+v: %v", remoteStorageLocation, err)
+			}
+			if err = pullMetadata(commandEnv, writer, dir, remoteStorageLocation, dir, remoteConf); err != nil {
+				return fmt.Errorf("cache metadata on %+v: %v", remoteStorageLocation, err)
 			}
 
 			// store a mount configuration in filer