🔒 fix(stdlib): enforce FileSystem capability checks in file.rs

[Tcode-Motion]

🎯 What: This PR fixes a security vulnerability in stdlib/src/file.rs where file operations (read, write, copy, remove, exists) were missing capability checks, unlike std.fs in sys.rs.
⚠️ Risk: Without these checks, untrusted or sandboxed scripts executed by the runtime could bypass file system restrictions using std.file.* functions, potentially leading to unauthorized reads, modifications, or deletions of arbitrary files accessible by the host process.
🛡️ Solution: Added a check for Capability::FileSystem at the beginning of each file operation callback. If the capability is not present in ctx.config.capabilities, a RuntimeError is returned. Additionally, updated the register_module metadata for "std.file" to explicitly require Capability::FileSystem.

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PR created automatically by Jules for task 8953389804118506594 started by @Tcode-Motion

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