[rsd-darshan]

Closes #630.

Remote string types whose From<&str> borrows or accepts only static strings could not use derive(ProtoString), and remote bytes wrappers always copied their wire payloads.

• Add copy_from_str = path to ProtoString, using the owning constructor for From<&str>, copy_from_str, and UTF-8-validated wire decoding.
• Add from_bytes = path to ProtoBytes, constructing from WirePayload::into_bytes() and setting PREFERS_OWNED_PAYLOAD = true so Bytes-backed input can share its allocation.
• Preserve existing defaults, owned conversions, and the independent as_shared hook. Document input-buffer retention and add a changelog fragment.

Validation:

• New constructor fixtures fail to compile before the change because the attributes are unsupported.
• Regression coverage includes non-static string inputs, invalid UTF-8, tuple/named wrappers, allocation identity through runtime decoding, borrowed input, invalid attributes, and serde/arbitrary compatibility.
• task lint passes.
• task test passes (4,328 tests passed; 206 ignored).

No buffa-codegen output or checked-in generated types change.

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