No direct AMPL/USDC UniswapV2 market exists on mainnet, so this oracle
bridges through WETH: AMPL/USDC = (AMPL/WETH) x (WETH/USDC), reporting an
18-decimal TWAP to a MedianOracle on the 24h rebase cadence. update() opens
the measurement window right after rebase (via the Orchestrator tx list,
gated to the daily update window) and pushReport() closes it ~2h before the
next rebase (gated by minReportTimeIntervalSec) so the report ages past the
MedianOracle security window.

- contracts/DexOracle.sol: per-leg UniswapV2 cumulative-price TWAP with
  on-chain decimals bridging; direction is a per-leg useToken1Price flag, so
  no inverse code is needed. unchecked blocks faithfully mirror UniswapV2
  by-design accumulator/uint32 wrapping (not expected operationally, but kept
  so a far-future wrap degrades gracefully instead of reverting). Constructor
  emits LogBridgeTokens for off-chain inspection (log-only, no revert: the two
  bridge-side tokens may legitimately be distinct equivalent tokens).
- _external/: minimal vendored IUniswapV2Pair + 0.8.4 UniswapV2OracleLibrary.
- mocks/: MockUniswapV2Pair, MockERC20Decimals, MockMedianOracle.
- test/unit/DexOracle.ts: decimals bridging, chained TWAP, accumulator
  wraparound, window/min-period gating, and revert paths (12 tests).
- scripts/deploy.ts: deploy:dexoracle task with verified mainnet pool
  defaults; re-reads token0()/token1() on-chain, optionally registers the
  provider and appends update() to the Orchestrator.

Mainnet token orderings verified via eth_call:
  AMPL/WETH 0xc5be99... token0=WETH token1=AMPL -> price1 (WETH per AMPL)
  USDC/WETH 0xb4e16d... token0=USDC token1=WETH -> price1 (USDC per WETH)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Address review feedback:

- TWAP conversion now follows the canonical fixed-window oracle: each leg's
  raw UQ112x112 cumulative is bridged to an 18-decimal price-seconds value at
  snapshot time (scale-then-diff), and the window average is the difference of
  two snapshots over the elapsed time.
- The period gate lives only on update(); the read/consult/report path no
  longer carries an Uniswap-example-style PERIOD_NOT_ELAPSED check. Added a
  consult() view that returns the live TWAP without any timing gate.
- Removed the inUpdateWindow time-of-day gating (it duplicated the
  MedianOracle's report-delay/expiration security window).

Access control:

- update(): the Orchestrator (settable, owner-managed) may call at any time;
  any other caller must wait `period` (default 22h = 24h rebase - 2h security
  delay) since the last update, preventing off-schedule window resets.
- pushReport(): fully open. It can only push the honest on-chain TWAP, so it
  needs no gate; MedianOracle aggregation/delay handle the rest.
- purgeReports(): onlyOwner (admin) passthrough to MedianOracle.purgeReports().

Tests cover the orchestrator bypass, the open pushReport, the period gate for
open callers, the uint32 timestamp wraparound, decimals bridging and the purge
passthrough (17 DexOracle tests; full suite 351 passing). The deploy task now
calls setOrchestrator when --orchestrator is provided.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>