docs: consolidate all docs under docs/ — single source of truth

Move issues (01–29) and PRD from .scratch/distributed-inference-network/
into docs/issues/ and docs/. Update ralph_progress.py DEFAULT_PRD path
and rewrite docs/agents/issue-tracker.md to reflect the new layout.

The distributed_inference_network.egg-info/docs/ mirror is a build
artifact already covered by *.egg-info/ in .gitignore — not committed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/issues/06-solana-stake-and-settlement.md

@@ -0,0 +1,32 @@
+Status: ready-for-agent
+
+# 06 — Solana stake + settlement contracts
+
+## What to build
+
+Deploy and integrate the Solana smart contracts that make node staking, client payment, and token reward settlement trustless. All development and testing targets **Solana testnet** — never devnet or mainnet during development, to avoid real costs.
+
+Three contracts are needed:
+
+**Registry contract**: records stake balances, strike counts, and ban status per wallet. The gateway and tracker read from this contract to exclude banned wallets from route selection.
+
+**Payment contract**: clients pre-fund an API key account with SOL or USDC. The gateway records per-request compute attribution (which node served which layer range, for how many tokens).
+
+**Settlement contract**: called once per epoch. Debits client accounts proportional to compute consumed. Credits node operator wallets with our native token proportional to layers served. Distributes a validator reward share.
+
+The `packages/contracts` package provides Python wrappers for reading and writing to all three contracts. The gateway uses these wrappers to check stake before routing to a node and to record attribution after each request.
+
+## Acceptance criteria
+
+- [ ] All contracts deploy successfully to Solana testnet
+- [ ] A node can submit a stake transaction and have its balance reflected in the registry contract
+- [ ] A client can fund an API key account with testnet SOL
+- [ ] After a completed inference session, compute attribution is recorded on-chain with correct node/layer attribution
+- [ ] The epoch settlement transaction correctly distributes token rewards to node operators and deducts client balances
+- [ ] The gateway refuses to route to a node whose stake balance is below the minimum threshold
+- [ ] All contract interactions in tests run against a local Solana test validator (via `solana-test-validator`) — no live testnet required for CI
+- [ ] A `.env.testnet` config points to Solana testnet RPC for manual end-to-end testing
+
+## Blocked by
+
+- `03-tracker-registration-and-routing.md`