rclone: add automated tests using the memory backend

[omar-polo]

Summary

• Add rclone/connector_test.go with 16 tests covering the full connector surface
• Use rclone's built-in memory backend for fully in-process testing (no network, no temp files, no fake FS overlay needed)
• Tests are structured to mirror the WebDAV integration test pattern

Tests added

Metadata / connectivity

• TestMetadata — verifies Type(), Origin(), Root()
• TestPing — verifies Ping() succeeds on a non-empty backend

Importer

• TestImport — walks a seeded tree, checks expected paths arrive on the records channel
• TestImportFileContent — opens a record's Reader and verifies file content

Exporter

• TestExport — creates a directory and a file, verifies the file lands in the rclone FS
• TestExportSkipsXattr — xattr records are ack'd without writing to the FS
• TestExportSkipsRoot — the / directory record is ack'd without calling Mkdir

Storage

• TestStorageCreateOpen — round-trips the CONFIG blob
• TestStorageCreateAlreadyExists — second Create returns an error
• TestStoragePutGetRoundtrip — subtests for packfile, state, and lock resources
• TestStoragePutGetRange — byte-range read returns the correct slice
• TestStorageList — two objects appear after two Puts
• TestStorageDelete — object disappears from List after Delete
• TestStorageUnsupportedResource — all four storage methods return an error for an unknown resource
• TestStorageMode — returns ModeRead|ModeWrite
• TestStorageSize — returns -1

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Generated by Claude Code

[omar-polo]

draft because i'd like to merge #47 before this goes in.