fix(keeper): distinguish storage failures from validation errors in SubmitPocValidationsV2

## Problem

`SubmitPocValidationsV2` used `LogWarn + continue` for all `SetPocValidationV2` errors,
treating infrastructure-level storage failures the same as expected validation errors
(e.g. invalid bech32 addresses). A transient storage failure would silently drop votes
and return success to the caller — leaving consensus state inconsistent with no observable signal.

## Fix

Replace `LogWarn + continue` with `LogError + return error` for `SetPocValidationV2` failures.

This is safe because `HasPocValidationV2` (called earlier in the same loop iteration)
already validates bech32 addresses for both participant and validator. Any error reaching
`SetPocValidationV2` is therefore definitively a storage-layer failure, not invalid input.

- Storage failure: `LogError` + abort batch via `return nil, fmt.Errorf(...)`.
  Cosmos SDK rolls back the full transaction, preventing partial writes.
- Invalid address: caught by `HasPocValidationV2` → `LogWarn + continue`.
  Partial-success design preserved. `TestSubmitPocValidationsV2_PartialSuccess` passes.

Adds `TestSubmitPocValidationsV2_StorageError_AddressPreValidation` documenting the
address pre-validation invariant that makes this distinction possible.

## Impact

- Storage failures are now observable (LogError, tx rollback) instead of silent
- Partial-success behavior for invalid addresses unchanged (design intent preserved)
- Closes #1012

Author: cisco

inference-chain/x/inference/keeper/msg_server_poc_v2_test.go

@@ -182,6 +182,31 @@ func TestSubmitPocValidationsV2_PartialSuccess(t *testing.T) {
 	require.True(t, exists2)
 }
 
+// TestSubmitPocValidationsV2_StorageError_AddressPreValidation documents the address
+// pre-validation invariant: HasPocValidationV2 validates bech32 addresses BEFORE
+// SetPocValidationV2 is called. Therefore any SetPocValidationV2 error is a storage failure.
+// This test verifies the invariant by showing SetPocValidationV2 with an invalid participant
+// address errors on bech32 decoding — and that this path is unreachable via the batch handler
+// (invalid addresses are already caught by HasPocValidationV2 at line 116).
+func TestSubmitPocValidationsV2_StorageError_AddressPreValidation(t *testing.T) {
+	k, ctx, _ := keepertest.InferenceKeeperReturningMocks(t)
+	sdkCtx := sdk.UnwrapSDKContext(ctx)
+
+	// Direct call: SetPocValidationV2 returns error for invalid participant bech32.
+	err := k.SetPocValidationV2(sdkCtx, types.PoCValidationV2{
+		ParticipantAddress:          "invalid_address",
+		ValidatorParticipantAddress: testutil.Validator,
+		PocStageStartBlockHeight:    100,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "bech32")
+
+	// In SubmitPocValidationsV2, this path is unreachable: HasPocValidationV2 validates
+	// the same addresses first (line 116) and returns continue on error.
+	// Therefore SetPocValidationV2 errors in the batch loop are definitively storage failures,
+	// not address validation errors — making return nil, fmt.Errorf the correct response.
+}
+
 // Test HasPocValidationV2
 func TestHasPocValidationV2(t *testing.T) {
 	k, ctx, _ := keepertest.InferenceKeeperReturningMocks(t)

inference-chain/x/inference/keeper/msg_server_poc_validations_v2.go

@@ -137,12 +137,18 @@ func (k msgServer) SubmitPocValidationsV2(goCtx context.Context, msg *types.MsgS
 			ValidatedWeight:             validation.ValidatedWeight,
 		}
 
+		// HasPocValidationV2 above already validated bech32 addresses for both participant
+		// and validator. Any error here is therefore a storage-layer failure, not invalid input.
+		// Abort the entire batch: a storage failure is infrastructure-level and partial writes
+		// would leave consensus state inconsistent. Cosmos SDK rolls back the tx on non-nil error.
 		if err := k.SetPocValidationV2(ctx, storedValidation); err != nil {
-			k.LogWarn("[SubmitPocValidationsV2] Failed to store validation, skipping", types.PoC,
+			k.LogError("[SubmitPocValidationsV2] storage failure, aborting batch", types.PoC,
 				"validator", msg.Creator,
 				"participant", validation.ParticipantAddress,
+				"storedSoFar", storedCount,
 				"error", err)
-			continue
+			return nil, fmt.Errorf("storage failure storing poc validation for participant %s: %w",
+				validation.ParticipantAddress, err)
 		}
 
 		storedCount++