fix(morpho): require 8-decimal upstream oracle (audit #187)

[hardyjosh]

MorphoProtocolAdapter.price() unconditionally scales latestAnswer() * 1e28, which is correct iff the upstream oracle reports 8 decimals.
OracleRegistry.setOracle() doesn't constrain decimals — a registry
swap to an 18-decimal feed (e.g. a future Chainlink integration) would
silently mis-price Morpho collateral by 10^10×. There is no observable
revert; Morpho would just see a wildly wrong number.

Adds:

• EXPECTED_ORACLE_DECIMALS constant (= 8) derived from the 36 - 8
  scaling exponent.
• UnexpectedOracleDecimals(uint8 actual, uint8 expected) error.
• A decimals() check at the top of price(), BEFORE latestAnswer()
  is read, so a misconfigured oracle fails loudly before the wrong
  number ever enters the computation.

Tests:

• testPriceRevertsOnNonEightDecimals — fuzz over every uint8 != 8 and
  assert the new revert fires with the right payload.
• testPriceDecimalsCheckRunsBeforeAnswer — mocks latestAnswer to
  revert; confirms the decimals check fires first.
• All four existing positive tests updated to mock oracle.decimals()
  to 8 (default-zero would now hit the new revert).
• AutoPausePropagation tests continue to pass — they use the real
  PythOracleAdapter which hardcodes decimals = 8.

Closes #187.

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com

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[hardyjosh]

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• fix(morpho): require 8-decimal upstream oracle (audit #187) #224 : 3 dependent PRs (#225 , #227 , #228 ) 👈 (View in Graphite)
• refactor(interface): rename to AggregatorV2V3Interface + add getRoundData #222 : 1 other dependent PR (#223 )
• chore: remove MultiPythOracleAdapter for Euler launch #238
• docs: README refresh + integrator notes for corporate-action auto-pause (RAI-325) #26 : 1 other dependent PR (#221 )
• feat(deploy): thread CorporateActionPauseConfig through unified deployers (RAI-322) #25
• test: auto-pause revert propagation through protocol adapters (RAI-321) #24
• feat(oracle): wire corporate-action auto-pause into BasePythOracleAdapter (RAI-320) #23
• feat(lib): LibCorporateActionsPause reader helper (RAI-319) #22
• docs(spec): corporate-action-aware auto-pause semantics (RAI-318) #21
• deps: migrate from git submodules to soldeer #237
• main

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