Add local FlowMemory devnet prototype

[FlowmemoryAI]

Summary

Adds a no-value local FlowMemory devnet/appchain prototype under the new chain bucket.

The prototype is a self-contained Rust CLI that models:

• deterministic genesis
• rootfields and latest roots
• artifact commitments
• work receipts
• verifier reports
• imported FlowPulse observations
• imported verifier reports
• deterministic blocks, state roots, block hashes, and tx ids
• Base settlement anchor placeholders
• local JSON persistence and fixture handoff exports

This advances #18, #35, #36, #37, #41, #49, #50, and #51 without adding production consensus, tokenomics, validator rewards, mainnet deployment, bridge contracts, or hardware validator assumptions.

Commands

cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- demo
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- inspect-state --summary
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- submit-fixture --fixture fixtures/handoff/sample-txs.json
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- run-block
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- export-fixtures --out-dir fixtures/handoff/generated

Checks Run

cargo fmt --manifest-path crates/flowmemory-devnet/Cargo.toml
cargo clippy --manifest-path crates/flowmemory-devnet/Cargo.toml -- -D warnings
cargo test --manifest-path crates/flowmemory-devnet/Cargo.toml

Manual smoke path also passed:

cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json reset-local
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json submit-fixture --fixture fixtures/handoff/sample-txs.json
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json run-block
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json submit-fixture --fixture fixtures/handoff/sample-flowpulse-observation.json
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json submit-fixture --fixture fixtures/handoff/sample-verifier-report.json
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json run-block
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json inspect-state --summary
cargo run --manifest-path crates/flowmemory-devnet/Cargo.toml -- --state devnet/local/smoke-state.json export-fixtures --out-dir fixtures/handoff/generated-smoke

Boundaries

• No production consensus.
• No tokenomics.
• No validator rewards, staking, or slashing.
• No mainnet deployment.
• No bridge security claims.
• No live Base settlement.
• No raw AI memory or artifacts on-chain.
• No hardware validator requirements.

Notes

The working tree had unrelated uncommitted work before this branch. This PR commit includes only the local devnet/appchain prototype files in the allowed scope.