feat(solana): add depin-attest — T1 DePIN attestation plugin (Track C ⭐)

[xinaids]

The $40 Pi that writes to Solana

Track C DePIN — depin-attest is the reference implementation for ZeroClaw's DePIN layer.

Custody tier: T1 — never holds a key, never calls sendTransaction.

What's in it

Component	Track	Tier	Summary
plugins/depin-attest	C — DePIN	T1	Reads a device sensor, builds unsigned Solana Memo tx with replay-guard nonce

Test table

Test	What it proves	Result
nonce_is_deterministic	same device+slot → same nonce	PASS
nonce_differs_by_slot	replay guard works across slots	PASS
nonce_differs_by_device	two devices can't collide	PASS
memo_format_includes_all_fields	output is compact <400 chars	PASS
tx_serializes_and_has_v0_prefix	valid versioned tx wire format	PASS
base64_roundtrip	encode is RFC 4648 compliant	PASS
prompt_injection_unknown_field_rejected	fail closed on extra fields	PASS
prompt_injection_sign_and_submit_ignored	no T2 path exists in crate	PASS
output_is_compact	summary <300 chars (no context flood)	PASS
replay_nonce_covers_slot_and_device	nonce entropy verified	PASS

10/10 PASS — cargo test --quiet

Bounty checklist

• Layout matches plugins/redact-text
• Pure core / thin shim
• Host tests, no wasm toolchain needed
• cargo build --target wasm32-wasip2 --release clean
• cargo clippy --all-targets + --target wasm32-wasip2 clean
• Structured logging via log-record
• Manifest with minimal permissions
• README: custody tier, threat model, wiring diagram, injection transcript
• MIT License

Work in progress — engaging in #solana-bounty on Discord.