fix(eth): passthrough JSON-RPC reads + tip-aware fee warning + drop-check diagnostic

[BitHighlander]

Summary

This PR is opened draft for auditing. It bundles four related fixes that together unblock the Uniswap "Confirm in wallet" hang plus the recurring stuck-pending-tx pattern. The three commits stack cleanly so reviewers can audit each independently.

The headline fix is the JSON-RPC shape passthrough — that's the smell that breaks the dApp's ability to track a tx after we hand back its hash, and it would still bite us on a perfect public-mempool RPC. See docs/RPC_PASSTHROUGH_AUDIT.md (vendored in this PR) for the field-by-field analysis.

Commits

1. fix(eth): passthrough eth_getTransaction* + eth_getBlockByNumber to preserve JSON-RPC shape (3256fce)

   • handleEthGetTransactionByHash, handleEthGetTransactionReceipt, handleEthGetBlockByNumber were calling ethers v6 wrapper methods that return class instances with renamed/dropped fields (gas/gasLimit, input/data, transactionIndex/index, flat vs nested v/r/s). Replaced with provider.send('<method>', params) passthroughs that return the spec shape verbatim. Mirrors the existing pattern in 9cf2bbe (eth_call + eth_estimateGas) on the read side.
   • Same commit also adds a post-broadcast drop-check (8s + 45s setTimeouts) that logs [DROP-CHECK] and emits chrome.runtime tx_drop_warning when the broadcast hash is invisible to our RPC. Diagnostic for the low-tip eviction failure mode.

2. feat(eth): tip-aware fee-warning + smart-contract detection fix (2f9a777)

   • Fee-warning now flags maxPriorityFeePerGas below per-chain tip floor (previously only checked maxFeePerGas floor). Tip economics matter independently — high maxFee with low tip = single-mempool acceptance, no propagation, eviction.
   • FeeWarning shape extended with trigger, priorityFloorWei, effectiveTipWei. Banner title varies by trigger.
   • RequestMethodCard was reading transaction.request.data, but transaction.request is the JSON-RPC params array — request.data is always undefined, so Universal Router calls (data: 0x3593564c…) rendered as a green-check 'Simple transfer'. Now reads transaction.unsignedTx.data to match the Details tab.

3. docs: RPC passthrough audit + dropped-tx retro (32b9399)

   • docs/RPC_PASSTHROUGH_AUDIT.md — the audit document, vendored as the source of truth for reviewers. Field-divergence tables, structured-clone consequences, list of handlers audited, audit candidates outside ethereumHandler.ts.
   • RETRO_uniswap_swap_dropped_tx.md — failure-mode retro that drove this work.

Audit asks

The reviewers I'd particularly like eyes from:

• Confirm the field-divergence table in docs/RPC_PASSTHROUGH_AUDIT.md against ethers v6 source. I derived it from inspection; a sanity-check pass would be valuable.
• Sanity-check the per-chain tip-floor numbers in feeFloors.ts (STATIC_PRIORITY_FLOOR_WEI). The mainnet 1 gwei is the load-bearing one for the failing case; others (Polygon 25 gwei, Avalanche 1 gwei, BSC 1 gwei, sequencer-driven L2s = 0) are conservative defaults that may want refinement.
• The drop-check uses fixed 8s + 45s timeouts. Reasonable, but if there's a preference for telemetry/configuration we can wire that through.
• Out of scope, separately tracked: EVM RPC URL bootstrap is still hardcoded in chains.ts and index.ts:665. Per discussion this should migrate to Pioneer (single source of truth for non-EVM already). Not patched here; captured in retro + memory. If this PR's reviewers can confirm the migration approach we'll start that workstream next.

What this PR does not fix

• The "tx drops from mempool" routing problem itself. Diagnostic only via the drop-check; root cause is upstream of what we control (RPC routing through providers like llamarpc that forward to private mempools).
• Vault firmware nonce display. Out of repo.

Test plan

• pnpm build clean (verified locally, all 9 packages green).
• Reload extension at chrome://extensions, swap small amount on Uniswap mainnet.
• After [HANDOFF] dApp ← KeepKey (ethereum/eth_sendTransaction) RESOLVE, expect the polling eth_getTransactionByHash response value to have JSON-RPC field names (gas, input, transactionIndex, flat v/r/s) — not the ethers wrapper shape (gasLimit, data, index, nested signature).
• Approval card should now read "Smart Contract — Interacts with smart contract — review carefully" (yellow) for Universal Router calls instead of green-check "Simple transfer".
• If tip is below 1 gwei (mainnet), expect orange banner with "⚠ Low miner tip — tx may be dropped" + footer line showing tip floor and effective tip.
• Background console after broadcast: [DROP-CHECK] tx 0x… visible on RPC at 8000ms (block=...) if mined, or [DROP-CHECK] tx 0x… not visible on RPC 45000ms after broadcast if dropped.

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